In 1969, Dutch broadcaster NTS told viewers to wrap TVs in what material?

In 1969, Dutch broadcaster NTS told viewers to wrap their televisions in aluminium foil.

The prank claimed that inspectors equipped with remote scanners would drive through Dutch streets searching for households that had not paid the radio and television licence fee. Viewers were told that covering their television or radio with aluminium foil would prevent the equipment from being detected.

The story was convincing enough to trigger a real public reaction. On the following day, supermarkets reportedly sold out of aluminium foil, while payments of the broadcasting tax increased. The joke therefore became a classic example of an April Fools' broadcast whose fictional technology produced measurable behaviour in the real world.

The foil did not actually provide a practical solution to licence enforcement, and the prank was not about protecting a television from ordinary signals. It played on contemporary anxieties about surveillance, household broadcasting fees and the mysterious power of electronic scanners.