A VAN television detector toured round Oxford for two weeks on the trot to hunt for people watching telly illegally.

On June 14 1960 a three-man team including a radio expert and a local Post Office official starting working on a list of 500 addresses where no record of a TV licence exists in order to figure how whether any unlicensed sets were being used.

To do so, they used the olive-green van – one of just nine in the entire country.

The van was kitted out with oddly-shaped aerials on its roof which can be manually moved separately to assist in pin-pointing the exact position of its sets.

The team had powers to ask residents to see their licenses, and where they are not or cannot be produced to take down the details which may lead to a prosecution.

The man in charge, Ron Smith explained that the system of deduction is straightforward but effective.

When a TV set is switched on it gives out a radio signal. The detector van then used its adapted radio receiver which is tuned to the wavelength of the signal and then converts it to a whistle transmitted through the technical officer's headphones.