The good wizard showed him his latest invention. It was a chastity belt... except that it had a rather large hole in the most obvious place.
'This is no good, Merlin!' the king exclaimed, 'Look at this opening. How is this supposed to protect m'lady, the Queen?'
'Ah, sire, just observe.' said Merlin. He then selected his most worn-out wand,and inserted it in the gaping hole of the chastity belt whereupon a small guillotine blade came out and cut the stick neatly in two.
'Merlin, you are a genius!' said King Arthur. After putting Guinevere in the device, King Arthur set out upon his Quest.
Several years passed before he returned to Camelot.
Upon arrival, he immediately assembled all his knights in the courtyard and had them drop their trousers for a 'short arm' inspection. Sure enough, each of them had an amputated little Johnny or was damaged in some way. All except Sir Galahad.
'Sir Galahad', exclaimed King Arthur, 'The one and only true knight! Only you among all the nobles have been true to me. What is it in my power to grant you? Name it and it is yours!'
Sir Galahad was speechless!