An exciting left-arm bowler of express pace, Mills has had a dramatic rise through the ranks after only starting to play cricket at the age of 14.
He made his first-class debut for Essex in June 2011 against the touring Sri Lankans and claimed the wicket of Tharanga Paranavitana.
Having already represented his country at under-19 level at the beginning of the year, he then took on Sri Lanka A in August as part of an England Development XI.
By the end of the summer, he had also featured in three LV= County Championship matches and one Clydesdale Bank 40 fixture for Essex.
He became a potential England Performance Programme player in September but next month was promoted to the main EPP party as an injury replacement and was toured Bangladesh with England Lions.
Mills returned career-best figures of 4-25 against Glamorgan in May 2012, taking 4-4 in a spell of 31 balls.