In 1986 it was donated to the care of the London Transport Museum, and from 1989 formed part of the LT Museum Collection.  It is retained in working order, in final London Transport condition, ie with an early standard radiator (red bar, no roundel) and ventilator front wings. It has occasionally been seen at rallies, and very occasionally meets up with the other prototypes. Having spent 38 years on other duties, RM1 was called back to revenue-earning passenger duties in February 1997, when it celebrated 40 years of Routemaster service in London by working on Route 2 to Crystal Palace for two days.  Since then it has appeared occasionally, notably during the festivities surrounding the withdrawal of Routemasters from normal service, and at special occasions such as the Bow Garage Centenary, operating in service.  Since 2009 it has appeared at various events in the south of England, as seen below
Information from: http://www.countrybus.org/RM/RM1.html