The details and routes of numbered services are set at around the year 1933. Some will have been extended and some curtailed before and after this date. So complete accuracy for any particular photograph cannot be guaranteed.

40

Plumstead (Wickham Lane)
Woolwich (Beresford Square)
Embankment (Savoy Street)
Extended to Wickham Lane weekday peak hours

Via:
Charlton
Greenwich
Deptford
New Cross
Peckham
Camberwell Green
Kennington
Westminster Bridge