Chris Webb:
Hi Chris.
Do you know anything more about this Mammoth Major KGY 788D,looks very much like an A E Evans ex Shell,the one next to it has a reg starting with NW which could be NWR Yorks West Riding and Evans had a few ex Harold Wood in that sequence.
The other photo was taken at Barking depot,the Mammoth Major was another ex Shell and the Mandator next to it was ex LPG Morley.
Hi Chris, thought when I found these you would be onto them 
Sadly no I have no info on KGY, I found it in amongst some other pics I’ve got & thought straight away ex Shell/BP/A E Evans so I put it on in case you recognised it! Chris