The next generation of red LT single-decker after the RF was represented by the Merlin (MB) and Swift (SM) classes, at one time the perceived solution to running an economic service in most of London.  They provided the new buses for the 'Reshaping Plan', introduced in 1968, having first been introduced on the central London Red Arrow services two years earlier.  The Merlins failed, partly due to unreliability, partly due to operational problems and partly because double-deck OMO became permitted and indeed encouraged by Government.  They didn't last long.

 

Meanwhile, the RFs were getting old, but there were certain routes that could not take larger buses - and neither could Kingston Garage, where the pits were unsuitable for 8' wide buses.  The choice was limited to one type - the Bristol LH, of identical dimensions to the RF.  In the views of some, they were a retrograde step, and (like most new buses in the 70s) they weren't as reliable as their predecessors.  But 95 were purchased in 1976-7, allowing RFs to be retired across London. 

 

In south London, they replaced RFs on Sutton's routes 80 and 80^A (although much of their work was to be replaced within months by double-deck DMSs on the 280 and 280^A), at Croydon on the 234^A and at Kingston - although not, ironically on the last two RF routes, where the problem of the pits was solved by moving the allocation to Norbiton and introducing Leyland Nationals.