Libelling someone in fiction

[Dr Jekyll]

Suppose I wrote a book in which a reprehensible character committing all sorts of crimes bore a clear resemblance to a famous person who hadn't actually been convicted of anything.

Might the real person sue, or would it be possible to say 'the names different so it wasn't you'? Would the mere fact of not wanting to suggest they resembled a villain be enough to stop them suing?
If there was a danger of being sued, could I protect myself by including a scene where my villain and the real life person were at the same event, thereby implying they weren't the same person?