Guisborough, Yorkshire born outside left Allan Codling began his football career with Whitby United before joining Bolton Wanderers. He played for Bolton’s reserve team in the Central League, but did not make their first team, and his contract was cancelled in January 1933. He immediately signed for Hartlepools United, and played for their reserves in the North Eastern League, but again didn’t make their first eleven before leaving the club at the end of the season.
He began the 1933-34 season with Midland League club Scarborough, and spent the next season with Gresley Rovers. While with Gresley he was chosen for the Central Combination select XI to play the champions, and had trials with Football League clubs Preston North End and Brighton & Hove Albion. Although a move to Brighton was reported to be well on the way to completion, Codling spent his next season with Southern League club Folkestone, where he made his debut in senior football in an FA Cup first round tie at Romford in November 1935.
He signed for Third Division (South) club Clapton Orient in the summer of 1937, setting up the opening goal on his Football League debut as Orient won 2-0 at Exeter City in September 1936. and he scored 3 times in 33 appearances over his two years with the club but after losing his place in November 1937 he made only one further appearance for Clapton Orient before leaving Brisbane Road in the summer of 1938, when he joined Third Division (North) club Darlington where he played more frequently for their reserves making 7 appearances, five of which were late in the season, and was selected for the Rest of the North Eastern League team for the match against the League champions in March 1939. He re-joined Hartlepools United in the summer of 1939 but hadn’t played for their first team by the time of the outbreak of the Second World War, which effectively ended his career.