Post 1406 is curious. MOF 227 (3207) was the last half cab bus - a Daimler with Crossley body of 1953 - to enter service with the BCT. Subsequent buses were demonstrators followed by the flat fronted fleet which made their appearance. It passed to the PTE in 1969. The last of the batch being withdrawn by the PTE in 1977. A black and white photograph could suggest its initial allocation to Acocks Green when new; it could also suggest a photo shot as suggested by OM.
Apart from one person behind the cab (conductor, inspector?) I cannot see anyone else on the bus.
I wondered if it was a driver under tuition, but see no 'L' plates or similar identification.
One other thought might be that the bus was being re-directed to fill a gap caused by another's failure or to cope with a sudden increase in passengers on one of the routes served by Acocks Green garage.
* Cue Hercules Poirot!