Cal McCord sits atop Ladybird in the foyer of the Gaumont Theatre in Shepherd’s Bush. This theatre was damaged during the war by a flying bomb, more infomation here.
The picture was shot with the doors behind the children, the trees of Shepherd’s Bush Common visible.
According to here Cal was an American ex-serviceman who remained in the UK becoming a cowboy actor and entertainer.
There is imdb entry which shows he did have roles through till the early 1972’s. There is also an interesting clip via the Pathe News archives of his stage act a decade earlier.
A young boy and girl are escorted by two police officers. This is the only frame of this scene on the negative strip featuring building shots of the area suggesting that the image is not set up. They are walking up the street toward West End Central Police Station