[5][6] As a junior for the Exeter Swimming Club, he competed at the British Winter Championship in 2000 at the age of 15.

[7] He competed at a senior level for the first time in 2005 at the 2005 World Aquatic Championships, where he took the bronze medal in the 50m backstroke.

[15] It was the second gold of the event for the British team, who took home their best ever tally of seven medals in total.

[12] As of 2010, he was ranked second in the world for the 50m backstroke and third for the 100m,[18] and following his success at the Commonwealth Games he was named BBC South West's Sportsman of the Year 2010.

[14] On 5 March 2012, Tancock won the 100m backstroke final at the British trials with a time of 53.16 seconds in the event held at the London Aquatics Centre.

[21] He also pushed around his coach's car in order to improve his stamina and transfer his 50m backstroke form to the 100m event.

[25] In November 2020, it was reported that Australia's Brenton Rickard tested positive for a banned substance which could lead to the GB Team being awarded a retrospective bronze medal.

[26] Tancock achieved the World Championships qualifying time, but the team coach only chose swimmers who had a chance of being at Rio 2016.

[27] At the age of 30, Tancock qualified for the final of the 100m backstroke at the World Aquatics Championships in a time of 53.19.

Liam is the younger of 2 boys born for mum Kim; his brother is 2 years older.