Before you can say Jack Robinson or sometimes, faster than you can say Jack Robinson, is one of the stranger British idioms. It means very quickly - I'll have your car valeted before you can say Jack Robinson.
Why Jack Robinson? Nobody knows for sure but there are some theories. It is first mentioned in Francis Grose's Dictionary of Vulgar Tongues in 1811, in which he suggests an impatient man, called Jack Robinson, would visit his neighbours and leave before his name could be announced.
Another theory is that it is based on a man called John Robinson who was Constable of the Tower of London 1660 - 1665 and would execute prisoners very quickly, or, before you could say Jack Robinson. They both seem rather unlikley but it's a fun idiom nonetheless.
While we're here, let's take a tour of the Tower of London.