Like most museums, the London Transport Museum can't put everything it owns on display, so keeps a lot in storage, and a few times a year, that store is opened to the public.The depot, next to the railway in Acton houses a number of old tube trains, including a never used concept train, a lot of old trams and some buses - but also an enormous collection of old bits of equipment from the past 160 years of public transport from tiny documents right up to huge electricity transformers and bits of old escalators.