Two minutes into the second half at the Mestalla on 25 June 1982 he scored the goal that beat the hosts and sent Northern Ireland through as group winners, held for half an hour with ten men after Mal Donaghy went off. He scored against Honduras, Spain and France that summer, more than any other British player at the tournament, won the British Home Championship in 1980 and 1984, and finished with 12 goals in 63 caps. Career record: 63 caps and 12 goals for Northern Ireland; club career at Tottenham Hotspur, Watford, RCD Mallorca.
| 1972–1975 | Bangor |
| 1975–1980 | Tottenham Hotspur |
| 1980–1983 | Watford |
| 1983–1985 | RCD Mallorca |
| 1985–1986 | West Bromwich Albion |
| 1986–1986 | Chesterfield |
| 1986–1989 | Brighton & Hove Albion |
| 1987–1987 | Millwall |
| 1989–1990 | Crawley Town |
| 1990–1991 | Bromley |
| 1990–1990 | Glenavon |
| 1991–1995 | Worthing |
| Northern Ireland | 63 caps, 12 goals |
Northern Ireland legends whose careers overlapped Armstrong's
One rank above: Gareth McAuley at #26.
One rank below: Maik Taylor at #28.
Northern Ireland's editorial top five: George Best · Danny Blanchflower · Pat Jennings · Peter Doherty · Aaron Hughes.