I was once told by a controller (in Centrewest London Buses days) that
the busiest in terms of passenger loadings was the 207 (Shepherds
Bush-Uxbridge). This route was recently (April 2005) renumbered into
two overlapping sections (207 and 427), although it had in fact been
running in these separate sections, albeit under the same route number,
for about 20 years. Presumably the renumbering and changes in
routes/travel patterns over time mean it has lost this distinction now?

Keith