Neil Williams wrote:

Unless it's changed, an early-morning Silverlink service from MK Central (or
probably Bletchley these days on a Saturday) to Euston is operated using a
pair of 150s to get them from Bletchley depot to London ready to operate on
the Barking-Gospel Oak line.

I've heard quite a few reports of 150s in Euston recently...When I was
at Euston on the 21st Oct, 150131 was stabled in Platform 17 -
http://photos.darrenjohnson.co.uk/p8532117.html doing very little (all
lights/engines off) this was at about 14:00