Hay started taking part in running competitions at an early age and competed for Aldershot, Farnham and District Athletics Club in 2003.

[1] Hay made his international debut for Great Britain in the 2009 season, starting with an appearance at the 2009 IAAF World Cross Country Championships in the junior race.

On the circuit he placed third in the junior 3000 m at the Aviva London Grand Prix and won the Gateshead leg of the UK Cross Challenge series.

[6] He started the 2012 season with his first senior level success against international competition: he was runner-up to Asbel Kiprop at the Great Edinburgh Cross Country, defeating Olympic medallists Eliud Kipchoge and Kenenisa Bekele in the process.

[7] He started studying chemistry at the University of Birmingham and proved himself in student competition with a win at the BUCS Cross Country.

He returned to the European Under-23 Cross Country race and managed fourth place – Britain's best performer – and led the British to the team silver medals behind Russia.