It is illegal here in the UK to not decrypt. I've always wondered how anyone could prove I knew what the key was. Would saying "too late, I have a dead man's sw

It is illegal here in the UK to not decrypt. I've always wondered how anyone could prove I knew what the key was. Would saying "too late, I have a dead man's switch that tripped while I was in custody" and showing that mechanism be enough? If so, I could just build a bogus mechanism. It's not really a situation one should play at :)