A Shepherds Bush native, Gallen established himself as something of a legend at QPR. He notched up over 400 appearances and hit 97 goals for the R's in two spells spanning nearly 14 years. Gallen joined Huddersfield 2000 and after 10 goals in 30 starts for the Terriers, Gallen moved across Yorkshire to join Barnsley the following summer, but the call of West London saw him return to QPR within a few months. He then scored nine goals in 16 league starts for MK Dons before joining Luton on loan.

After a successful loan spell Gallen joined permanently in January 2009.

The striker enjoyed a prolific season in non-league football with his football know-how often too good for opposition defences. He struck-up a partnership with Tom Craddock and finished the campaign with 21 goals in all competitions.

Remarkably, given the length and success of his time in the game, it therefore came as a surprise when he revealed that his hat-trick in the 6-0 win over Grays Athletic in April 2010, was the first of his career.