Obviously when quite new, 1955.
But look to the left; an 1890s GSWR 6-wheeled first class saloon, possibly now downgraded, with a much newer bogie behind it. Such was the contrast readily and regularly available.
Thanks again guys. Very encouraging words also. I'm on the right track and it reassures me that spending more time on the prep won't be wasted by a catastrophic paint job. I was expecting all manner of bleed but only had it in one or two spots at the coach ends where a touch up will be under the weathering later anyway.
I watched quite a few YouTube videos about all this before having a go. The Everard Junction respray videos are a good resource for example. Galgorm Hall also had some useful info.