How funny are the Edinburgh Festival Fringe's top 15 jokes?

Cambridge University dropout Ken Cheng is the winner of this year's Edinburgh Fringe funniest joke competition.
Funniest joke winner Ken Cheng.Funniest joke winner Ken Cheng.
Funniest joke winner Ken Cheng.

Cheng, who quit the university to play poker professionally before breaking into comedy two years ago, topped the poll of 15 gags. And here they are: