Mike, it appears that it doesn't work!
It beggars belief, Ken, that a Government Department should have authorised and built, with taxpayers money, this Heath Robinson / Fred Karno's Circus dumb-waiter* lash up - it's not much more advanced than flinging a bucket and a rope out of the window to haul up your sandwiches, [ apart from the money squandered ], is it? And to have to disassemble it weekly to allow an inspector to examine the scaffolding clamps is absolutely bloody preposterous!!! No wonder the tax hike in the UK now exceeds 42% of ones' gross earnings.
What's wrong with bribing a few trusty inmates with some snout* to carry the food upstairs, on trays*, up some stairs*?
*snout. Tobacco; UK prison currency.
*tray. A shallow box with handles for carrying stuff.
*stairs. A series of steps arranged at about 42 degrees so folks can safely climb or descend between floors, with minimum effort or hinderance.
*dumb-waiter. An electrician checking the mail daily for his free hat.