[1] He had a breakthrough in 2010, when he broke the English Schools' Athletics Association Championships record in the final of the 1500 metres as well as taking the title.

[2] He went on from this to win bronze at the 2010 Summer Youth Olympics in the 1000 metres, after coming second at the European Trials event in Russia.

In 2012 he broke Steve Ovett's British junior mile record, running 3:57.90 at the London Grand Prix in Crystal Palace as part of the Diamond League.

He then won British U23 and Senior 1500 metres titles, before going to Beijing at the end of August to compete in the World Championships.

[10] At the IAAF Diamond League meeting on 11 July 2019, in Monaco, Grice set another PB of 3:30.62, to overtake Steve Ovett on the all-time list, placing him fourth, behind Sebastian Coe, Steve Cram and Mo Farah.