On Mar 15, 8:23*pm, Dominic wrote:
I often see London Overground Class 378s stabled in the sidings
between platforms 15 and 16 at Euston. Do these Class 378s simply
travel to Euston from Willesden because the depot is short of space,
or are these units doing test running? I did not notice until today
that these sidings do not have platforms.
Thanks, Dominic

It's all for night-time test running purposes - more specifically, for
the accumulation of fault-free mileage before they go into full
passenger service. I'll leave it to others more expert than I to
correct most of what I've said...!