Allied|Willow Road, Hampstead — the quiet street where a marriage is put under surveillance

After Casablanca, the Vatans come home to a London hill and try to live like other people. The exteriors of that ordinary life were shot around Willow Road and Christchurch Hill in Hampstead, a few streets of brick and stucco that climb steeply from the Heath toward the village.

The choice was practical. These roads have kept their proportions — low garden walls, sash windows, the same iron railings — so a period dresser only needs to remove the parked cars and swap the street lamps. The camera sets up looking west, up the incline, and the hill does the rest of the work.

Willow Road has one famous building of its own. Number 2 is Ernő Goldfinger's modernist house of 1939, now owned by the National Trust and open to visitors; it was going up at almost exactly the moment the film is set, which makes the street an odd little collision of the war Allied is about and the architecture that came out of it.

Walk up from the Heath entrance at the bottom rather than down from the tube. You arrive the way the surveillance men in the film would have arrived, on foot and slightly out of breath, watching front doors. The neighbourhood is entirely residential — look, don't linger on doorsteps — and the pull of the scene is precisely that nothing here looks like it could hold a secret.