46256 worked to Nuneaton on the 4K55 1430 Brent – Crewe (Nuneaton dep. 1710) from Willesden, but on arrival had low coal level in the front of the tender. The fireman was not permitted to climb into the tender due to the electrified OHL, so an electric loco provided assistance to Crewe.

This Image shows E3029 backing onto train.
The other image shows E3029 ready to depart, with pantographs reversed and correct Route Indicator number displayed.

There were plenty of spare electric locos at Nuneaton, as three days earlier, March 2, saw the commencement of electric hauled northbound passenger & freight workings from Nuneaton, where engine changes took place.
May 1964 RO reports that up to 8 electrics can be seen stabled waiting to take over northbound trains, so more than likely the image of E3029 with others in sidings was taken on same day.