Anyone travelling to and from Paddington on the GWR has probably
noticed the growing number of Elizabeth Line trains parked in the OOC
Depot sidings. But I had a closer look from a footbridge over the
nearby canal:

https://www.flickr.com/photos/recliner/albums/72157695029566492

The trains on view in the 33 stabling roads are the full 9-car length,
and are identified as Elizabeth Line, not TfL Rail, so they're
obviously in storage until December 2018. There's room for many more
trains there, some of which will be the TfL Rail 7-car sets currently
in use, but others might be as yet undelivered 9-car ones.