A question from dating photos ... when were totems installed? A reference I have suggests "as from 1948" implying that they were being put in very soon indeed after nationalisation. Is that true, or did it take a while for standardisation to start replacing the alternatives that the big 4 had used until that time?

Other standards seemed to take time - locomotive (and other rolling stock?) production lines still made locomotives of the old company's classes, for example, and a couple of timetables I have from soon after nationalisation look like the old company's product with a very thin veneer of British Rail.