diff --git a/src/calibre/devices/mtp/filesystem_cache.py b/src/calibre/devices/mtp/filesystem_cache.py
index 99c961a228..fd5e5cd8e9 100644
--- a/src/calibre/devices/mtp/filesystem_cache.py
+++ b/src/calibre/devices/mtp/filesystem_cache.py
@@ -17,7 +17,7 @@ from calibre.utils.icu import sort_key, lower
 
 class FileOrFolder(object):
 
-    def __init__(self, entry, fs_cache, all_storage_ids):
+    def __init__(self, entry, fs_cache, all_storage_ids=()):
         self.object_id = entry['id']
         self.is_folder = entry['is_folder']
         self.name = force_unicode(entry.get('name', '___'), 'utf-8')
@@ -28,7 +28,7 @@ class FileOrFolder(object):
         self.parent_id = entry.get('parent_id', None)
         if self.parent_id == 0:
             sid = self.storage_id
-            if sid not in all_storage_ids:
+            if all_storage_ids and sid not in all_storage_ids:
                 sid = all_storage_ids[0]
             self.parent_id = sid
         if self.parent_id is None and self.storage_id is None:
@@ -68,11 +68,19 @@ class FileOrFolder(object):
             yield e
 
     def add_child(self, entry):
-        ans = FileOrFolder(entry, self.id_map)
+        ans = FileOrFolder(entry, self.fs_cache())
         t = self.folders if ans.is_folder else self.files
         t.append(ans)
         return ans
 
+    def remove_child(self, entry):
+        for x in (self.files, self.folders):
+            try:
+                x.remove(entry)
+            except ValueError:
+                pass
+        self.id_map.pop(entry.object_id, None)
+
     def dump(self, prefix='', out=sys.stdout):
         c = '+' if self.is_folder else '-'
         data = ('%s children'%(sum(map(len, (self.files, self.folders))))
diff --git a/src/calibre/devices/mtp/test.py b/src/calibre/devices/mtp/test.py
index 6595a330d4..705d9bdd2a 100644
--- a/src/calibre/devices/mtp/test.py
+++ b/src/calibre/devices/mtp/test.py
@@ -9,14 +9,80 @@ __docformat__ = 'restructuredtext en'
 
 import unittest
 
+from calibre.utils.icu import lower
 from calibre.devices.mtp.driver import MTP_DEVICE
+from calibre.devices.scanner import DeviceScanner
 
-class Test(unittest.TestCase):
+class TestDeviceInteraction(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        cls.dev = MTP_DEVICE(None)
+        cls.dev.startup()
+        cls.scanner = DeviceScanner()
+        cls.scanner.scan()
+        cd = cls.dev.detect_managed_devices(cls.scanner.devices)
+        if cd is None:
+            raise ValueError('No MTP device found')
+        cls.dev.open(cd, 'test_library')
+        if cls.dev.free_space()[0] < 10*(1024**2):
+            raise ValueError('The connected device %s does not have enough free'
+                    ' space in its main memory to do the tests'%cd)
+        cls.dev.filesystem_cache
+        cls.storage = cls.dev.filesystem_cache.entries[0]
+
+    @classmethod
+    def tearDownClass(cls):
+        cls.dev.shutdown()
+        cls.dev = None
 
     def setUp(self):
-        self.dev = MTP_DEVICE(None)
+        self.cleanup = []
 
     def tearDown(self):
-        pass
+        for obj in reversed(self.cleanup):
+            self.dev.delete_file_or_folder(obj)
 
+    def test_folder_operations(self):
+        ''' Test the creation of folders, duplicate folders and sub folders '''
+
+        # Create a folder
+        name = 'zzz-test-folder'
+        folder = self.dev.create_folder(self.storage, name)
+        self.cleanup.append(folder)
+        self.assertTrue(folder.is_folder)
+        self.assertEqual(folder.parent_id, self.storage.object_id)
+        self.assertEqual(folder.storage_id, self.storage.object_id)
+        self.assertEqual(lower(name), lower(folder.name))
+
+        # Create a sub-folder
+        name = 'sub-folder'
+        subfolder = self.dev.create_folder(folder, name)
+        self.assertTrue(subfolder.is_folder)
+        self.assertEqual(subfolder.parent_id, folder.object_id)
+        self.assertEqual(subfolder.storage_id, self.storage.object_id)
+        self.assertEqual(lower(name), lower(subfolder.name))
+        self.cleanup.append(subfolder)
+
+        # Check that creating an existing folder returns that folder (case
+        # insensitively)
+        self.assertIs(subfolder, self.dev.create_folder(folder,
+            'SUB-FOLDER'),
+            msg='Creating an existing folder did not return the existing folder')
+
+        # Check that creating folders as children of files is not allowed
+        root_file = [f for f in self.dev.filesystem_cache.entries[0].files if
+                not f.is_folder]
+        if root_file:
+            with self.assertRaises(ValueError):
+                self.dev.create_folder(root_file[0], 'sub-folder')
+
+def tests():
+    return unittest.TestLoader().loadTestsFromTestCase(TestDeviceInteraction)
+
+def run():
+    unittest.TextTestRunner(verbosity=2).run(tests())
+
+if __name__ == '__main__':
+    run()
 
diff --git a/src/calibre/devices/mtp/unix/driver.py b/src/calibre/devices/mtp/unix/driver.py
index ae6975a746..09bb9ccace 100644
--- a/src/calibre/devices/mtp/unix/driver.py
+++ b/src/calibre/devices/mtp/unix/driver.py
@@ -12,6 +12,7 @@ from threading import RLock
 from io import BytesIO
 from collections import namedtuple
 
+from calibre import prints
 from calibre.constants import plugins
 from calibre.devices.errors import OpenFailed, DeviceError
 from calibre.devices.mtp.base import MTPDeviceBase, synchronous
@@ -157,34 +158,31 @@ class MTP_DEVICE(MTPDeviceBase):
     def filesystem_cache(self):
         if self._filesystem_cache is None:
             with self.lock:
-                files, errs = self.dev.get_filelist(self)
-                if errs and not files:
-                    raise DeviceError('Failed to read files from device. Underlying errors:\n'
-                            +self.format_errorstack(errs))
-                folders, errs = self.dev.get_folderlist()
-                if errs and not folders:
-                    raise DeviceError('Failed to read folders from device. Underlying errors:\n'
-                            +self.format_errorstack(errs))
-                storage = []
+                storage, all_items, all_errs = [], [], []
                 for sid, capacity in zip([self._main_id, self._carda_id,
                     self._cardb_id], self.total_space()):
-                    if sid is not None:
-                        name = _('Unknown')
-                        for x in self.dev.storage_info:
-                            if x['id'] == sid:
-                                name = x['name']
-                                break
-                        storage.append({'id':sid, 'size':capacity,
-                            'is_folder':True, 'name':name})
-                all_folders = []
-                def recurse(f):
-                    all_folders.append(f)
-                    for c in f['children']:
-                        recurse(c)
-
-                for f in folders: recurse(f)
-                self._filesystem_cache = FilesystemCache(storage,
-                        all_folders+files)
+                    if sid is None: continue
+                    name = _('Unknown')
+                    for x in self.dev.storage_info:
+                        if x['id'] == sid:
+                            name = x['name']
+                            break
+                    storage.append({'id':sid, 'size':capacity,
+                        'is_folder':True, 'name':name, 'can_delete':False,
+                        'is_system':True})
+                    items, errs = self.dev.get_filesystem(sid)
+                    all_items.extend(items), all_errs.extend(errs)
+                if not all_items and all_errs:
+                    raise DeviceError(
+                            'Failed to read filesystem from %s with errors: %s'
+                            %(self.current_friendly_name,
+                                self.format_errorstack(all_errs)))
+                if all_errs:
+                    prints('There were some errors while getting the '
+                            ' filesystem from %s: %s'%(
+                                self.current_friendly_name,
+                                self.format_errorstack(all_errs)))
+                self._filesystem_cache = FilesystemCache(storage, all_items)
         return self._filesystem_cache
 
     @synchronous
@@ -223,16 +221,42 @@ class MTP_DEVICE(MTPDeviceBase):
         return tuple(ans)
 
     @synchronous
-    def create_folder(self, parent_id, name):
-        parent = self.filesystem_cache.id_map[parent_id]
+    def create_folder(self, parent, name):
         if not parent.is_folder:
-            raise ValueError('%s is not a folder'%parent.full_path)
+            raise ValueError('%s is not a folder'%(parent.full_path,))
         e = parent.folder_named(name)
         if e is not None:
             return e
-        ans = self.dev.create_folder(parent.storage_id, parent_id, name)
+        ename = name.encode('utf-8') if isinstance(name, unicode) else name
+        sid, pid = parent.storage_id, parent.object_id
+        if pid == sid:
+            pid = 0
+        ans, errs = self.dev.create_folder(sid, pid, ename)
+        if ans is None:
+            raise DeviceError(
+                    'Failed to create folder named %s in %s with error: %s'%
+                    (name, parent.full_path, self.format_errorstack(errs)))
+        ans['storage_id'] = sid
         return parent.add_child(ans)
 
+    @synchronous
+    def delete_file_or_folder(self, obj):
+        if not obj.can_delete:
+            raise ValueError('Cannot delete %s as deletion not allowed'%
+                    (obj.full_path,))
+        if obj.is_system:
+            raise ValueError('Cannot delete %s as it is a system object'%
+                    (obj.full_path,))
+        if obj.files or obj.folders:
+            raise ValueError('Cannot delete %s as it is not empty'%
+                    (obj.full_path,))
+        parent = obj.parent
+        ok, errs = self.dev.delete_object(obj.object_id)
+        if not ok:
+            raise DeviceError('Failed to delete %s with error: '%
+                (obj.full_path, self.format_errorstack(errs)))
+        parent.remove_child(obj)
+
 if __name__ == '__main__':
     BytesIO
     class PR:
diff --git a/src/calibre/devices/mtp/unix/libmtp.c b/src/calibre/devices/mtp/unix/libmtp.c
index 1c92e6d13f..620d1afe46 100644
--- a/src/calibre/devices/mtp/unix/libmtp.c
+++ b/src/calibre/devices/mtp/unix/libmtp.c
@@ -118,6 +118,34 @@ static uint16_t data_from_python(void *params, void *priv, uint32_t wantlen, uns
     return ret;
 }
 
+static PyObject* build_file_metadata(LIBMTP_file_t *nf, uint32_t storage_id) {
+    char *filename = nf->filename;
+    if (filename == NULL) filename = "";
+
+    return Py_BuildValue("{s:k,s:k,s:k,s:s,s:K,s:O}",
+                "id", nf->item_id,
+                "parent_id", nf->parent_id,
+                "storage_id", storage_id,
+                "name", filename,
+                "size", nf->filesize,
+                "is_folder", (nf->filetype == LIBMTP_FILETYPE_FOLDER) ? Py_True : Py_False
+    );
+}
+
+static PyObject* file_metadata(LIBMTP_mtpdevice_t *device, PyObject *errs, uint32_t item_id, uint32_t storage_id) {
+    LIBMTP_file_t *nf;
+    PyObject *ans = NULL;
+
+    Py_BEGIN_ALLOW_THREADS;
+    nf = LIBMTP_Get_Filemetadata(device, item_id);
+    Py_END_ALLOW_THREADS;
+    if (nf == NULL) dump_errorstack(device, errs);
+    else {
+        ans = build_file_metadata(nf, storage_id);
+        LIBMTP_destroy_file_t(nf);
+    }
+    return ans;
+}
 // }}}
 
 // Device object definition {{{
@@ -188,9 +216,7 @@ libmtp_Device_init(libmtp_Device *self, PyObject *args, PyObject *kwds)
         }
     }
 
-    // Note that contrary to what the libmtp docs imply, we cannot use
-    // LIBMTP_Open_Raw_Device_Uncached as using it causes file listing to fail
-    dev = LIBMTP_Open_Raw_Device(&rawdev);
+    dev = LIBMTP_Open_Raw_Device_Uncached(&rawdev);
     Py_END_ALLOW_THREADS;
 
     if (dev == NULL) { 
@@ -328,117 +354,65 @@ libmtp_Device_storage_info(libmtp_Device *self, void *closure) {
     return ans;
 } // }}}
 
-// Device.get_filelist {{{
-static PyObject *
-libmtp_Device_get_filelist(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
-    PyObject *ans, *fo, *callback = NULL, *errs;
-    ProgressCallback cb;
-    LIBMTP_file_t *f, *tf;
+// Device.get_filesystem {{{
 
-    ENSURE_DEV(NULL); ENSURE_STORAGE(NULL);
+static int recursive_get_files(LIBMTP_mtpdevice_t *dev, uint32_t storage_id, uint32_t parent_id, PyObject *ans, PyObject *errs) {
+    LIBMTP_file_t *f, *files;
+    PyObject *entry;
+    int ok = 1;
 
+    Py_BEGIN_ALLOW_THREADS;
+    files = LIBMTP_Get_Files_And_Folders(dev, storage_id, parent_id);
+    Py_END_ALLOW_THREADS;
 
-    if (!PyArg_ParseTuple(args, "|O", &callback)) return NULL;
-    if (callback == NULL || !PyCallable_Check(callback)) callback = NULL;
-    cb.obj = callback;
+    if (files == NULL) return ok;
 
-    ans = PyList_New(0);
-    errs = PyList_New(0);
-    if (ans == NULL || errs == NULL) { PyErr_NoMemory(); return NULL; }
+    for (f = files; ok && f != NULL; f = f->next) {
+        entry = build_file_metadata(f, storage_id);
+        if (entry == NULL) { ok = 0; }
+        else {
+            PyList_Append(ans, entry);
+            Py_DECREF(entry);
+        }
 
-    Py_XINCREF(callback);
-    cb.state = PyEval_SaveThread();
-    tf = LIBMTP_Get_Filelisting_With_Callback(self->device, report_progress, &cb);
-    PyEval_RestoreThread(cb.state);
-    Py_XDECREF(callback);
-
-    if (tf == NULL) { 
-        dump_errorstack(self->device, errs);
-        return Py_BuildValue("NN", ans, errs);
-    }
-
-    for (f=tf; f != NULL; f=f->next) {
-        fo = Py_BuildValue("{s:k,s:k,s:k,s:s,s:K,s:k,s:O}",
-                "id", f->item_id,
-                "parent_id", f->parent_id,
-                "storage_id", f->storage_id,
-                "name", f->filename,
-                "size", f->filesize,
-                "modtime", f->modificationdate,
-                "is_folder", Py_False
-        );
-        if (fo == NULL || PyList_Append(ans, fo) != 0) break;
-        Py_DECREF(fo);
+        if (ok && f->filetype == LIBMTP_FILETYPE_FOLDER) {
+            if (!recursive_get_files(dev, storage_id, f->item_id, ans, errs)) {
+                ok = 0; 
+            }
+        }
     }
 
     // Release memory
-    f = tf;
+    f = files;
     while (f != NULL) {
-        tf = f; f = f->next; LIBMTP_destroy_file_t(tf);
+        files = f; f = f->next; LIBMTP_destroy_file_t(files);
     }
 
-    if (callback != NULL) {
-        // Bug in libmtp where it does not call callback with 100%
-        fo = PyObject_CallFunction(callback, "KK", PyList_Size(ans), PyList_Size(ans));
-        Py_XDECREF(fo);
-    }
-
-    return Py_BuildValue("NN", ans, errs);
-} // }}}
-
-// Device.get_folderlist {{{
-
-int folderiter(LIBMTP_folder_t *f, PyObject *parent) {
-    PyObject *folder, *children;
-
-    children = PyList_New(0);
-    if (children == NULL) { PyErr_NoMemory(); return 1;}
-
-    folder = Py_BuildValue("{s:k,s:k,s:k,s:s,s:O,s:N}",
-            "id", f->folder_id,
-            "parent_id", f->parent_id,
-            "storage_id", f->storage_id,
-            "name", f->name,
-            "is_folder", Py_True,
-            "children", children);
-    if (folder == NULL) return 1;
-    PyList_Append(parent, folder);
-    Py_DECREF(folder);
-
-    if (f->sibling != NULL) {
-        if (folderiter(f->sibling, parent)) return 1;
-    }
-
-    if (f->child != NULL) {
-        if (folderiter(f->child, children)) return 1;
-    }
-
-    return 0;
+    return ok;
 }
 
 static PyObject *
-libmtp_Device_get_folderlist(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
+libmtp_Device_get_filesystem(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
     PyObject *ans, *errs;
-    LIBMTP_folder_t *f;
+    uint32_t storage_id;
+    int ok = 0;
 
     ENSURE_DEV(NULL); ENSURE_STORAGE(NULL);
 
+    if (!PyArg_ParseTuple(args, "k", &storage_id)) return NULL; 
     ans = PyList_New(0);
     errs = PyList_New(0);
     if (errs == NULL || ans == NULL) { PyErr_NoMemory(); return NULL; }
 
-    Py_BEGIN_ALLOW_THREADS;
-    f = LIBMTP_Get_Folder_List(self->device);
-    Py_END_ALLOW_THREADS;
-
-    if (f == NULL) {
-        dump_errorstack(self->device, errs);
-        return Py_BuildValue("NN", ans, errs);
+    LIBMTP_Clear_Errorstack(self->device);
+    ok = recursive_get_files(self->device, storage_id, 0, ans, errs);
+    dump_errorstack(self->device, errs);
+    if (!ok) {
+        Py_DECREF(ans);
+        Py_DECREF(errs);
+        return NULL;
     }
 
-    if (folderiter(f, ans)) return NULL;
-    LIBMTP_destroy_folder_t(f);
-
     return Py_BuildValue("NN", ans, errs);
 
 } // }}}
@@ -477,13 +451,13 @@ libmtp_Device_get_file(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
 // Device.put_file {{{
 static PyObject *
 libmtp_Device_put_file(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
-    PyObject *stream, *callback = NULL, *errs, *fo;
+    PyObject *stream, *callback = NULL, *errs, *fo = NULL;
     ProgressCallback cb;
     uint32_t parent_id, storage_id;
     uint64_t filesize;
     int ret;
     char *name;
-    LIBMTP_file_t f, *nf;
+    LIBMTP_file_t f;
 
     ENSURE_DEV(NULL); ENSURE_STORAGE(NULL);
 
@@ -500,26 +474,9 @@ libmtp_Device_put_file(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
     PyEval_RestoreThread(cb.state);
     Py_XDECREF(callback); Py_DECREF(stream);
 
-    fo = Py_None; Py_INCREF(fo);
     if (ret != 0) dump_errorstack(self->device, errs);
-    else {
-        Py_BEGIN_ALLOW_THREADS;
-        nf = LIBMTP_Get_Filemetadata(self->device, f.item_id);
-        Py_END_ALLOW_THREADS;
-        if (nf == NULL) dump_errorstack(self->device, errs);
-        else {
-            Py_DECREF(fo);
-            fo = Py_BuildValue("{s:k,s:k,s:k,s:s,s:K,s:k}",
-                    "id", nf->item_id,
-                    "parent_id", nf->parent_id,
-                    "storage_id", nf->storage_id,
-                    "name", nf->filename,
-                    "size", nf->filesize,
-                    "modtime", nf->modificationdate
-            );
-            LIBMTP_destroy_file_t(nf);
-        }
-    }
+    else fo = file_metadata(self->device, errs, f.item_id, storage_id);
+    if (fo == NULL) { fo = Py_None; Py_INCREF(fo); }
 
     return Py_BuildValue("NN", fo, errs);
 
@@ -549,11 +506,10 @@ libmtp_Device_delete_object(libmtp_Device *self, PyObject *args, PyObject *kwarg
 // Device.create_folder {{{
 static PyObject *
 libmtp_Device_create_folder(libmtp_Device *self, PyObject *args, PyObject *kwargs) {
-    PyObject *errs, *fo, *children, *temp;
+    PyObject *errs, *fo = NULL;
     uint32_t parent_id, storage_id;
     char *name;
     uint32_t folder_id;
-    LIBMTP_folder_t *f = NULL, *cf;
 
     ENSURE_DEV(NULL); ENSURE_STORAGE(NULL);
 
@@ -561,39 +517,13 @@ libmtp_Device_create_folder(libmtp_Device *self, PyObject *args, PyObject *kwarg
     errs = PyList_New(0);
     if (errs == NULL) { PyErr_NoMemory(); return NULL; }
 
-    fo = Py_None; Py_INCREF(fo);
-
     Py_BEGIN_ALLOW_THREADS;
     folder_id = LIBMTP_Create_Folder(self->device, name, parent_id, storage_id);
     Py_END_ALLOW_THREADS;
+
     if (folder_id == 0) dump_errorstack(self->device, errs);
-    else {
-        Py_BEGIN_ALLOW_THREADS;
-        // Cannot use Get_Folder_List_For_Storage as it fails
-        f = LIBMTP_Get_Folder_List(self->device);
-        Py_END_ALLOW_THREADS;
-        if (f == NULL) dump_errorstack(self->device, errs);
-        else {
-            cf = LIBMTP_Find_Folder(f, folder_id);
-            if (cf == NULL) {
-                temp = Py_BuildValue("is", 1, "Newly created folder not present on device!");
-                if (temp == NULL) { PyErr_NoMemory(); return NULL;}
-                PyList_Append(errs, temp);
-                Py_DECREF(temp);
-            } else {
-                Py_DECREF(fo);
-                children = PyList_New(0);
-                if (children == NULL) { PyErr_NoMemory(); return NULL; }
-                fo = Py_BuildValue("{s:k,s:k,s:k,s:s,s:N}",
-                        "id", cf->folder_id,
-                        "parent_id", cf->parent_id,
-                        "storage_id", cf->storage_id,
-                        "name", cf->name,
-                        "children", children);
-            }
-            LIBMTP_destroy_folder_t(f);
-        }
-    }
+    else fo = file_metadata(self->device, errs, folder_id, storage_id);
+    if (fo == NULL) { fo = Py_None; Py_INCREF(fo); }
 
     return Py_BuildValue("NN", fo, errs);
 } // }}}
@@ -603,12 +533,8 @@ static PyMethodDef libmtp_Device_methods[] = {
      "update_storage_info() -> Reread the storage info from the device (total, space, free space, storage locations, etc.)"
     },
 
-    {"get_filelist", (PyCFunction)libmtp_Device_get_filelist, METH_VARARGS,
-     "get_filelist(callback=None) -> Get the list of files on the device. callback must be callable accepts arguments (current, total)'. Returns files, errors."
-    },
-
-    {"get_folderlist", (PyCFunction)libmtp_Device_get_folderlist, METH_VARARGS,
-     "get_folderlist() -> Get the list of folders on the device. Returns files, errors."
+    {"get_filesystem", (PyCFunction)libmtp_Device_get_filesystem, METH_VARARGS,
+     "get_filesystem(storage_id) -> Get the list of files and folders on the device in storage_id. Returns files, errors."
     },
 
     {"get_file", (PyCFunction)libmtp_Device_get_file, METH_VARARGS,
diff --git a/src/calibre/devices/mtp/windows/driver.py b/src/calibre/devices/mtp/windows/driver.py
index e0a6219de0..7a01bf19b9 100644
--- a/src/calibre/devices/mtp/windows/driver.py
+++ b/src/calibre/devices/mtp/windows/driver.py
@@ -154,7 +154,7 @@ class MTP_DEVICE(MTPDeviceBase):
                         name = s['name']
                         break
                 storage = {'id':storage_id, 'size':capacity, 'name':name,
-                        'is_folder':True}
+                        'is_folder':True, 'can_delete':False, 'is_system':True}
                 id_map = self.dev.get_filesystem(storage_id)
                 for x in id_map.itervalues(): x['storage_id'] = storage_id
                 all_storage.append(storage)
@@ -247,7 +247,7 @@ class MTP_DEVICE(MTPDeviceBase):
     def get_file(self, object_id, stream=None, callback=None):
         f = self.filesystem_cache.id_map[object_id]
         if f.is_folder:
-            raise ValueError('%s is a folder on the device'%f.full_path)
+            raise ValueError('%s is a folder on the device'%(f.full_path,))
         if stream is None:
             stream = SpooledTemporaryFile(5*1024*1024, '_wpd_receive_file.dat')
         try:
@@ -262,14 +262,28 @@ class MTP_DEVICE(MTPDeviceBase):
         return stream
 
     @same_thread
-    def create_folder(self, parent_id, name):
-        parent = self.filesystem_cache.id_map[parent_id]
+    def create_folder(self, parent, name):
         if not parent.is_folder:
-            raise ValueError('%s is not a folder'%parent.full_path)
+            raise ValueError('%s is not a folder'%(parent.full_path,))
         e = parent.folder_named(name)
         if e is not None:
             return e
-        ans = self.dev.create_folder(parent_id, name)
+        ans = self.dev.create_folder(parent.object_id, name)
         ans['storage_id'] = parent.storage_id
         return parent.add_child(ans)
 
+    @same_thread
+    def delete_file_or_folder(self, obj):
+        if not obj.can_delete:
+            raise ValueError('Cannot delete %s as deletion not allowed'%
+                    (obj.full_path,))
+        if obj.is_system:
+            raise ValueError('Cannot delete %s as it is a system object'%
+                    (obj.full_path,))
+        if obj.files or obj.folders:
+            raise ValueError('Cannot delete %s as it is not empty'%
+                    (obj.full_path,))
+        parent = obj.parent
+        self.dev.delete_object(obj.object_id)
+        parent.remove_child(obj)
+