This looks like cars lined up outside a building, which to me looks like an airport because of the flags along the top of the building. It’s likely that this is Heathrow Airport and the picture was taken before a family holiday. Of the cars in the photo, I believe I recognise a Mini, a Ford Popular, a Morris Minor and a Ford Zodiac and the car with the registration 831 TPH is, I think, a triumph Herald, although it could also be a Hillman Imp.

Taken on Kodachrome slide film in the summer of 1963 and processed in October 1963.