But what is it and how does it work?

The envelope rule, introduced with the addition of Continental Europeans to the match in 1979, comes into effect in the event that one of the players gets injured during the course of the contest and is unable to compete in Sunday’s final singles session.

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In one of the more obscure Ryder Cup traditions, the opposing captain can select one player from his team that he would like not to compete. The nominated player is then matched up with the injured player and the match is recorded as a half.

There is, of course, a catch. The captains must place the name of their nominated player in an envelope prior to the start of the singles matches.

The names are a closely guarded secret and are only revealed if they are used. Captains hand them over when the singles draw is made and, if they are not required, the envelopes are destroyed so that no-one will ever know who the “benched” players would have been.

There have only been a few recorded instances of the envelope having been needed.

In 1991, Steve Pate was too sore from a traffic accident on the Wednesday of Ryder Cup week to play on the Sunday. European captain Bernard Gallacher had chosen to bench David Gilford, and so the Englishman sat out the match, with both teams getting a half-point.

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Most recently, in 1993, Lanny Wadkins offered to ‘take one for the team’ and actually volunteered himself for the envelope. Captain Tom Watson duly obliged and when Sam Torrance couldn’t play due to a sore left foot, Wadkins sat out the final session.

Incidentally, the same rule exists in the Presidents but not in the Solheim Cup.