I agree that the Flying Scotsman is probably the most famous, in its traditional 10am from Kings Cross slot. I am rather disapointed that the 10am from Kings Cross is no longer the Flying Scotsman, East Coast's biggest mistake probably. Unfortunately it isn't just a simple matter of restoring the name to the train, as the Northern Lights has nicked the 10am slot. A great shame.
That's East Coast's other big mistake, branding a loco and DVT as the Flying Scotsman when they will inevitably spend alot more of their time on other services than on the Flying Scotsman. Unfortunately removable head boards suitable for today's pointy locomotives would be rather difficult, but that hasn't stopped First Great Western putting up window stickers with the train name on, and an associated logo (although the window stickers appeared to be missing the time I rode "The Red Dragon"). East Coast also use window stickers to list calling points, but sadly they don't seem to have the train name on them(at least, when I caught what I think was the Northern Lights (which arrived in Aberdeen in time to catch the 17:21 to Inverness I saw no indication whatsoever that it was a named train).