Aged 20, he wrote his first work, The Rebel Child, which won the Grand Prize of the Society of Artists in France.

The first part of an intended trilogy, Excalibur blended musical styles and was performed by Roger Hodgson (ex-Supertramp), Fairport Convention, Dan Ar Braz, Tri Yann, Angelo Branduardi, Didier Lockwood and Gabriel Yacoub.

[citation needed] Five concert performances took place between October 1999 and June 2000, including one at Paris-Bercy.

In 2003, he created GAIA (Universal / BMG / Sony), a humanitarian concept album dealing with the preservation of the environment.

Guests included Midnight Oil, Justin Hayward of The Moody Blues, Zucchero, Jane Birkin, Cesaria Evora, Billy Preston.

In 2007, Simon released the second part of "Excalibur", Excalibur II, l'anneau des Celtes (Excalibur II, the ring of the Celts) with contributions from Jon Anderson (Yes), Alan Parsons, Barclay James Harvest, Maddy Prior, Jacqui McShee, John Wetton, Justin Hayward, Flook, Karan Casey, Fairport Convention, Andreas Vollenweider and Martin Barre.

Following this surprising success, "Excalibur" toured throughout Germany and 100,000 spectators attended the Celtic rock opera, reuniting nearly 160 musicians and almost as many technicians.

The Excalibur team performed a fourth arena tour in Germany and Switzerland 1–16 December 2016.

[4] As part of the science fiction festival "Les Utopiales" in Nantes on 3 November 2017, Simon created a symphonic electro-rock ballet entitled "Big Bang", about the beginning of the universe, with John Helliwell (from Supertramp fame) on saxophone.

[5] A new version of his folk rock opera "Tristan & Yseult" was performed at the Minsk National Theater in Belarus from 1 December 2017 to 2018.