Manchester United were the favourites, as Brighton had been relegated from the First Division that season, and had never reached a cup final before. United had finished third in the league that season and already had four FA Cup victories to their name.

The final ended in a 2–2 draw, forcing a replay at Wembley five days later, which Manchester United won 4–0.

The first match finished 2–2 after extra time. Gordon Smith and Gary Stevens scored for Brighton; Frank Stapleton and Ray Wilkins for United. The first game is famous for the radio commentary by Peter Jones "...and Smith must score" talking about a shot by Gordon Smith, which was then saved by the Manchester United goalkeeper Gary Bailey; the quote was subsequently used as a title for a Brighton fanzine. Bailey's save forced a replay and prevented Brighton from winning the first major trophy in their history.

The second game, on the Thursday night, started the same way as the first game had, with Brighton taking the game to Manchester United. Although their chances were limited to long-range drives from Jimmy Case, United goalkeeper Gary Bailey had a couple of important saves to make. This all changed on 25 minutes, with United's first real attack. Alan Davies, who had made his FA Cup debut in the first game, set up captain Bryan Robson for a left-footed drive past Moseley into the corner of the net. Suddenly the atmosphere changed and it was the Manchester United fans who were singing loudest. This was compounded in the 30th minute, when United went 2–0 up, giving the team a two-goal cushion for the first time over the two matches. Brighton failed to clear a corner, and Davies crossed for Norman Whiteside to score with a header, making the new 18 year old (just 19 days after his birthday) the youngest player to ever score (current to 2016 Final) in an FA Cup Final. This capped an incredible 12 months for the teenager, who had played in the 1982 FIFA World Cup Finals for Northern Ireland, and who had scored in the League Cup Final defeat to Liverpool earlier in the season.

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Wikipedia