The film starred Oscar-winning actor Hugh Griffith, Windsor Davies, Dewi "Pws" Morris and Sion Probert.

Four men, members of a Welsh rugby union club, fly to Paris as part of a weekend outing to see Wales play France in the Five Nations Championship match that will decide the Grand Slam title.

One of the party is funeral director Caradog Lloyd-Evans (Griffith), who briefly served in occupied Paris near the end of World War II.

Sion Probert plays camp boutique owner Maldwyn Pugh, who is the only one of the main four characters who makes the start of the match, because Mog is still in jail as he was considered the ringleader (the others were released), Caradog has collapsed near his strip club table while Glyn is trying for his own sexual 'Grand Slam' with Odette, taking a rest to watch the game on TV.

Originally the film was to run for 75 minutes, but just a few days before its first network broadcast on 17 March 1978, it was ordered to be cut down to an hour as a result of industrial action (a prelude to the Winter of Discontent).