Trevor.
The dieseline would have browned off the yellow much as WD40 will brown colours. Yellow never seemed to be a particularly durable colour on the BG 800s and 830s.
Why didn't PB steam clean the locos and maybe PK can tell us what they did at Pt. Lincoln?
Ian
There were a lot of things different at Peterborough. For example, D servicing was done over two days rather than one as it was at Mile End except I can remember a loco being late in and doing a C service in an afternoon including bedding and testing of generator brushes which was about a 25 minute job in itself... that was heavy going! Maybe it was in deference to the nature of the railway that a loco could be in as late as an afternoon and still expected out. Mile End always had the locos ready of a morning and cool if not cold for 5 days a week of heavier servicing.
I cannot answer with any degree of authority why the dieseline was used... maybe steam was ineffective on the local grits or perhaps it was a carry over from steam days when dieseline was less than 10c a gallon and water was needed for locos?
Open floor for now...
Trevor