J1491 - The Class 33 is still in green with a white stripe, and full yellow ends that wrap round to the cab side windows.
This was not an uncommon livery variation, but as the loco number looks to end in 1 (as far as I can see from zooming in) that limits the possibilities to 6501, 6561 or 6581...
By assuming that you'd unlikely to find an EH (Eastleigh) loco on a freight that originates deep into HG (Hither Green) territory, that eliminates 6501