Sewell, his wife Simone Lanham and creative manager Tim Rogers created Incognito Artists in London in 2000.

Sewell became an international classical crossover star in the so-called "opera band" Amici Forever[4][5] before leaving the singing group in 2006 and embarking upon a solo career.

The original line-up consisted of two tenors (Sewell, David Habbin), a baritone-bass (Nick Garrett), and two soprano singers (Jo Appleby, Tsakane Valentine).

He has sung for the late Queen Elizabeth II, King Charles III, Princes William and Harry and members of the Royal Family at the Royal Albert Hall, Windsor Castle and other venues; Nelson Mandela; and various celebrities such as Elton John, Leonardo DiCaprio and Victoria and David Beckham.

[9][10] Despite the success of Amici Forever, Sewell left the group suddenly after his eldest daughter Sienna was diagnosed with an autism spectrum disorder (ASD) in 2006.

[9][11] He sidelined his music career for a couple years before releasing his solo album debut, Believe, produced by Nick Patrick, in 2008.

[15] Sewell was a boy soprano in the school choir,[16] and later took singing lessons from New Zealand opera singer Geoffrey De la Tour while working in Wellington as a chartered accountant.