The Routemaster RML 3, as it was originally designated, was the third prototype built in 1956 by MCW in its Weymann factory at Addlestone, Surrey. It was registered SLT58 and taken into stock by LT in 1957. It had a short career and was used for driver training. It suffered an accident in 1959 and was retired in 1972.
The "L" designation was meant to identify it as having a Leyland engine but, to avoid confusion, this was dropped in 1961 when the "L" was used instead to identify lengthened Routemasters that were increased to thirty feet by the inclusion of a centre panel that provided eight additional seats.
There were many differences between RM3 and production Routemasters the most obvious of which was the bonnet being made of fibreglass and hinged to the inner side rather than the rear. The vehicle is now restored and preserved at the London Bus Museum at Brooklands.
And here is RM3 pictured, by Brian Burgess, alongside RM2 (left in its LT Country Bus green livery) at the 60th Anniversary weekend held at Finsbury Park in July 2014. (Note: In the right-hand image it is shown sporting the original RML 3 designation.)
Yes the left-hand image is RML 3 incognito. Why? I don't know; though I am given, on good authority, that it is a bus! Ed.
(see RM3 under construction here)
Here is RM3 pictured at Chancery Lane in 1978 (Image © Basil Hancock).
And here is RM3 pictured being exhibited at Syon Park on the 17th September 1978 (Image ©
Here are three of the prototype Routemasters pictured on the 25th September 1983 at LT's Aldenham Works (Images © Basil Hancock).