Click to ENLARGE and read here. Wikipedia: en.wikipedia.org/wiki/Operation_Hurricane
HMS Plym (K271), built in 1943, that served as a detonating platform. Click to ENLARGE.
The U.K. thus became the 3rd Nuclear Power after the U.S.A. and Russia.
It was just over 11-months before I was born. I think many people now forget that WE, THE BRITISH, are a very capable Nuclear Power.
That the explosion was conducted aboard a ship was interesting — befitting us being an Island nation. They, the U.S. and us, wanted to see what would happen if a nuclear bomb was detonated aboard a ship — in harbor. That was a real fear during the Cold War.