Whatever the first rule of cool, the first rule of funny is that if you try to dissect why a joke is funny in a solicitor's office, not only does funny move on, it doesn't leave a forwarding address and gets a restraining order taken out preventing you from ever contacting it again.

BBC: At last. A judge rules on what is - and will remain - cool

If a comedian tells a joke that you find funny, you laugh.

CNN: If you don't want to hear an edgy joke, don't listen

He was a funny fellow and always had a joke ready.

BBC: Reg Presley of The Troggs dies aged 71

If he tells a joke you do not find funny, don't laugh.

CNN: If you don't want to hear an edgy joke, don't listen

You wouldn't laugh during a conference where the boss says quarterly earnings are at an all-time low but you would laugh if the boss told a funny (or at least he thinks it's funny) joke.

CNN: Dealing with tears at work