OUTLINE : Give each participant (tower, or person, or household, or...) a full can of drink - beer, coke, tonic or whatever seems appropriate....

Stick a label onto the base asking them to enjoy the contents, then wash out the can and use it as a money collecting tin, to be returned to you when full again. Of course this must be kept within the household or belfry, - not waved around on street corners!

A normal size drink-can can hold as much as £90 or so depending on generosity of collectors and type of coins put in. (There is no rule against enlarging the hole to take £1 pieces!)

Keep a note of who has cans so you can 'call them in' after a suitable time even if not full.