[6] Reardon ran as part of the British 4x400m relay team at the 2022 World Athletics Indoor Championships.

[9][10][11] He was subsequently selected for the Great Britain squad for the European Indoor Championships held in Istanbul from March 2, 2023.

[13] He was selected as part of the Great Britain team for the 2023 European Athletics U23 Championships held from in July 2023 in Espoo, Finland.

[16] In January 2024, he pulled a hamstring which kept him out of competitive action for a number of months and could not take part in the British Olympic trials.

[19] Reardon was called-up as a late replacement for the Great Britain 4x400 metres relay squad for the 2024 Summer Olympics following the withdrawal of Charlie Carvell due to a hamstring injury.