Closest, but not close. UK's "independent" nuclear deterrant is British made warheads in British made submarines, but the missiles fired from those subs and to which those warheads are attached, are American.

https://en.wikipedia.org/wiki/Trident_(missile)

Still, plenty of times the UK has gone to bite, only to metaphorically boinked on the nose by a rolled up newspaper. Notably the Suez crisis.