 A right-handed batsman and a left-arm slow bowler, he started his cricket career at Northamptonshire, who finished in fourth position in the County Championship in his debut season, 1956.Allen debuted against Worcestershire in May and played in more than half the matches in the season.In 1957, Allen moved into a regular first-team place and finished high in the bowling averages, as Northamptonshire finished second in the County Championship table.