The film was made and release around one to two years after its source novel "Seven Days to a Killing" by Clive Egleton had been first published in 1973.
At the start of the film where the van is blown up on the motorway, it becomes clear that the scene is filmed on an incomplete stretch of motorway (possibly the M3, which was completed in 1974) as lane markings are missing from one carriageway.
In the roof garden where Tarrant's wife sends the toy fire engine down the slide towards him, as Tarrant turns to re-enter the house, the reflection of the boom mic can briefly be seen in the glass doors behind.