After the war, everything was destroyed, Watson said.
But though the games themselves are gone, their legacy is a source of pride for the makers of Monopoly, past and present.
"Since Charles Darrow created Monopoly in the 1930s, the game has had a rich and interesting story. The use of Monopoly by the British government to sneak maps, money and supplies to prisoners of war during World War II is a little-known, but important part of our history," said a spokeswoman for toymaker Hasbro, Inc. "We are always honored when this iconic game becomes an important part of the fabric of a family's, or a country's, history and memories."
In the 1970s, Watson had the chance to meet a few former POWs who actually used Wadddington's maps to escape from a prisoner camp at Colditz Castle, near Leipzig, Germany.
"It was really exciting," he said. Although it's impossible to know precisely how many prisoners escaped with the help of the hidden maps, experts estimate that about 35,000 members of the British, Commonwealth and U.S. forces who were taken prisoner during the war returned to Allied lines before the end of the war.
"We reckon that 10,000 used the Monopoly map," Watson said.