On 15 April 1984, Cooper collapsed from a heart attack in front of millions of television viewers, midway through his act on the live London Weekend Television (LWT) ITV variety show Live From Her Majesty's. Most of the audience thought it was part of his act and were laughing, until it became apparent he was seriously ill.

For a long time, a rumour circulated that the size 13 feet from his 6 foot 3 frame protruded underneath the curtains. While the show continued, efforts were being made backstage to revive Cooper, not made easier by the darkness. It was not until a second commercial break that ambulancemen were able to move his body to Westminster Hospital, where he was pronounced dead on arrival.