Ignition key for Post Office Television Detector Van. The van was built by Post Office engineering between 1974 and 1983, based on a Dodge SpaceVan.

Detector vans were designed by the GPO at Dollis Hill to enforce the television licensing system. The system began on the 1st June 1946, costing £2 for one channel in black and white, and the first TV detector van was unveiled on 1st February 1952. By the time this van was in action, there were 12 million TV licenses in the UK costing £4 each.

The BBC never said how these vans worked, but it was believed they detected electromagnetic radiation given off by the TV (although more often the authorities would simply find out who owned a TV from TV salespeople).

The vans were first demonstrated in 1952 at Earl’s Court radio show, and the technology behind the van was certainly functional. The detectors could detect TV’s from 100ft and successfully located 90% of TV’s in the UK in 1953. However, they were never particularly widely distributed and, despite remaining in TV license adverts as a threat into the eighties, most felt they were more effective as a deterrent than devices for actual detection.