Signed during the summer of 2013, Allan is a vastly experienced goalkeeper having played at the top level for Rangers and represented Scotland on a number of occasions.
After progressing through the youth ranks with Rangers, Allan made his first team debut in 2002 and although loan spells with St Johnstone and Dunfermline followed, he went on to establish himself as the first choice keeper at Ibrox, eventually making more than 200 appearances and winning three Scottish Premier League titles, three Scottish Cups and five Scottish League Cups.
His time in Glasgow also saw Allan play in the Champions League and UEFA Cup, and progress into a full Scottish international.
When financial problems hit Rangers in 2012, Allan opted to join Turkish side Besiktas and after a season playing in the Turkish Superleague, he arrived at the KC Stadium to sign for the Tigers.
A back injury which required surgery meant Allan missed the first half of the 2016/17 season, before joining Cardiff City on loan in January.