Christmas Special of A Question of Sport

[GoKartMozart]

Did anybody watch this show and if so, what please was the answer to a question that came out of the 'Christmas Cracker' round, roughly: Something invented by an American which was first used at the Wimbledon Tennis Championships in 1974. Unfortunately one of the children decided to be noisy at the point when the correct answer was being given, and though I've been trawling the web ever since, I still haven't found out.

[daftgrandad]

Use of Ties Breaks

[GoKartMozart]

I'm afraid that's not correct according to Wikipedia. They've got tie breaks at Wimbledon as being introduced in 1971.

[another-view]

That was the answer. I wouldn't believe everything you read on wikipedia