Finishing the 2009 season with a modest personal best time of 2:32.64 in the 200 metres breaststroke, Wilby took a chunk off this in May, swimming a 2:26.60 to qualify for the National Youth Championships.

In the final, Wilby swam the best race of his life so far, again surpassing his PB and winning the National 15/16 years title in an impressive 2:20.13.

[10] At the 2018 European Aquatics Championships, Wilby won heat four in the 100 metre breaststroke in a new personal best time of 59.12 qualifying second fastest for the final in 59.23.

In the final, Wilby set a personal best time of 58.64 to win the silver medal,[11] and became the equal fourth fastest 100m breaststroker in history; behind Brendan Rickard (58.58), Cameron Van Der Burgh's Olympic Gold from 2012 (58.44) and the winner of the European 100m title itself, Adam Peaty, who won in a world record time of 57.10*.

[23] At the 2022 World Aquatics Championships held in Budapest, Wilby won a bronze as part of the team in Men's 4 × 100 metre medley relay.

[24] At the 2022 Commonwealth Games, Wilby pulled off a surprise win in 100 m breaststroke, beating reigning champion Adam Peaty to fourth.

[26] Wilby won the 200 metres breaststroke at the 2024 Aquatics GB Swimming Championships[27] and was subsequently named in the British team for the 2024 Summer Olympics.

[28] Wilby's 100 metres breaststroke personal best of 58.46 puts him second on the British all-time list behind world record holder Adam Peaty.