I was very surprised to see a Freightliner Class 66 was due through Cradley running light engine from Stoke Gifford to Rugeley and return. As there would just about be enough light for a photo it was worth a shot. From what I can gather, it might be a diversionary route for coal trains when the Severn Tunnel is closed for maintenance.
Link to photos (only 2)
Here’s one, in full dull with bright sky – not good!