26th December 1986- Division One, Luton Town 0 Watford 2

In response to hooliganism, in particular the riot at the FA Cup Quarter Final between the Hatters and Millwall, Luton banned all away fans from attending games at Kenilworth Road from the start of the 1986/87 season. This was the first game where the ban affected Watford fans. It would eventually be lifted at the end of the 1989/90 season.

http://watford.fcdb.info/index.php?page=matches
Daily Telegraph, 27 Dec 1986
The Guardian, 27 Dec 1986
https://www.soccerbase.com/matches/results.sd?date=1986-12-26
https://www.11v11.com/league-tables/league-division-one/26-december-1986/