United Counties UC250, 250FRP, the first 36 foot vehicle in the fleet, a Bristol RELH6G/ECW DP47F, new in 1964 and bought specially for the express routes into London Victoria Coach Station.
To the left are three Standerwick double-deck Atlantean coaches (see the higher resolution picture if you want to see them all) and to the right, two keen bus spotters.

Photo taken Thursday 21 May 1964, Victoria Coach Station