In message , Richard J.
writes

Given some of the how-the-hell-did-they-get-there type places we've
all seen graffiti I suspect it won't be too much of a challenge for
them

Well, it was easy enough the first time. Those cars were newly painted
when they were placed on the viaduct, and the graffiti appeared very
soon afterwards.

From the pictures I saw, they were very much in the same condition they
left Uxbridge sidings in - a bit grimy but bare metal and mostly no
graffiti, although there was a little.
--
Steve Fitzgerald has now left the building.
You will find him in London's Docklands, E16, UK
(please use the reply to address for email)