[Kilsimpaile]

The other thing that I recall carried the death penalty in Britain was "high treason", which was a vague crime that could potentially include having a sexual relationship with a woman who was in line for producing an heir.

I recall that this was particularly relevant in the allegations of marital infidelity for Princess Diana. She couldn't have been charged but anybody apart from Prince Charles who had an affair with her could conceivably have been.

I don't know how seriously the law was taken though. I imagine it might be one of those centuries-old laws that live on because nobody overturned them.