He has hosted several television programmes including Real Rescues (2007–2013), Who Dares Wins (2007–2019), Break the Safe (2013–2014), 5-Star Family Reunion (2015–2016), and DIY SOS (1999–present).

After another family move to Deakin Leas in Tonbridge, he attended the Skinners' School in Tunbridge Wells, Kent,[6] where he passed eight O-levels, and excelled at Rugby.

[5] He played in bands from the age of 14 and was constantly writing music, poetry and comedy, until he submitted a script to a BBC2 programme that invited children to make a video.

Knowles has also hosted several entertainment programmes for the BBC since signing an exclusive contract with them,[3] including Who Dares Wins,[8] Last Choir Standing,[8] Guesstimation,[8] Secret Fortune,[8] and Perfection.

In 2009, Knowles co-presented the BBC reality TV series Wildest Dreams with James Honeyborne, in which novice candidates had to complete a set of challenging tasks filming wild animals in Africa.

In 2015, Knowles began presenting a new BBC One National Lottery game show 5-Star Family Reunion, which returned for a second series in 2016.

[12] From April 2019 he presented the BBC show Home Is Where the Art Is, in which he challenges three artists to create beautiful artwork for people they've never met.

[14] A week later, the BBC announced that they had resolved the issue and Knowles will return to his DIY SOS role with filming to resume in the coming months and is expected to be back on screens in 2022.

[16] In September 2024 Knowles was a contestant on the twenty-second series of BBC's Strictly Come Dancing, partnered with professional dancer Luba Mushtuk.

[19] Knowles was a co-writer on the film Golden Years, which stars Simon Callow, Virginia McKenna and Una Stubbs.