Come and 'ave a go if you think you're 'ard enough!
John and Mary have fallen in love, via the Internet, and John wishes to send Mary a ring. Unfortunately they live in a country where anything sent through the mail will be stolen unless it is enclosed in a padlocked box.
John and Mary each have plenty of padlocks, but none to which the other has a key. How can John get the ring safely into Mary's hands?
Answers on a postcard to the usual address please.
