tl;dr - this'll keep the ruddy blighters from nicking everything in the canteen.

Or not. Let us hand the microphone to an unnamed contributor at Wikipedia, who volunteered to tell the tale.

At the end of the war in Europe in 1945, France, Britain, United States and Russia agreed at the Potsdam Conference to split Germany into four occupation zones. The British area was occupied by the 21st Army Group that was collectively known as the British Army of the Rhine (BAOR).

The Allies' job was challenging. They had to disband and disarm the German fighting machine, reassemble the country's basic infrastructure, and cope with population on the brink of starvation. To this end the BAOR operated as a country within a country, requiring a monetary system that functioned to serve the needs of the occupying forces.

However, a problem soon emerged; goods intended for the troops were being sold to a thriving black market among the local population at highly inflated prices. Millions of pounds sterling were being lost by the taxpayers of Britain. A series of stopgap measures slowed, but did not stop the problem. It was decided in March 1946 that special military voucher system was needed.

Did it work? Well, don't let the suspense gnaw your innards through; hit next.