Route 240 was introduced in the 1930s between Edgware and Golders Green and replaced the former London General Omnibus Company Route 104. Initially it was split into two sections, the Mill Hill Broadway station to Edgware section being operated by single-deck TDs (seen here) and the Mill Hill to Golders Green section by double-deck RTs. This was because of the low railway bridge over Mill Hill Broadway which is seen in this view.
Photo by Geoff Plumb