Routemaster - RMC4
RMC4 (or CRL4 C=Coach, R=Routemaster, L=Leyland 4=4th prototype [but 3rd delivered]) was built by Eastern Coachworks in Lowestoft with Leyland supplied engine, gearbox and running units.
It entered service on the Greenline Country routes .
See (http://www.countrybus.org/RM/RM4.html) for an excellent description of the RMC4.
Here is RMC4 pictured at Leyland's 90th anniversary on the 17th May 1986 (Image © Basil Hancock).