Thanks for your extra comments guys. The colour is Humbrol paint No20, I suppose deep crimson, haven't checked that ..
I had ( inherited ..) three never opened largish No 4 size tins, which a friend had bought for the frames of a model loco build, the tins were maybe 25 years old.
I'd wondered if the then paint formulation might be more tweaked for brushing, which I wanted to try and use. Did a few trials, stirred it with a mini-drill very thoroughly. The paint seemed fine, and the brushing went ahead. The coats are somewhat translucent, looked a bit starved after just a few coats, with the primer / filler grinning but some more, gentle, rubbing down and more coats bulked it up, and the paint flowed quite nicely. It was partly having this crimson paint to hand that edged me towards the colour choice! I'd wondered if it was a bit of a bold option, but I think it's worked !
John, yes, I will certainly be keeping this engine. Hope that there may be some future enthusiasm for it within the family, but anyway, it pleases me to have it here.
I have added a brief section just now to the much older build notes ( referred to at the start of this "article" ), that I wrote up about this engine. Dave