According to a former flatmate, "Three things already stood out in him at the age of seventeen: his prodigious talent as an artist – he could paint original work in the style of any of the grand masters; his natural ability as a musician – he could pick out any tune on the piano by ear; and his zany sense of humour – he idolized the comedian Jerry Lewis."

He was studying drama at the Royal Academy of Dramatic Art when his college rock band, The Beatcrackers, were signed to a recording contract in 1963 as Mark Rogers and the Marksmen by EMI producer Norman Newell.

[2] In 1966, he wrote and produced the single "A Touch of Velvet – A Sting of Brass", an orchestral production credited to The Mood-Mosaic with vocals by the Ladybirds, which became a popular theme tune on pirate radio stations.

Working at Abbey Road Studios alongside the Beatles and Pink Floyd, often with engineer Geoff Emerick, Wirtz wrote and produced landmark recordings by artists such as Keith West, Tomorrow,[4] and Kippington Lodge.

Associations with Larry Page's Penny Farthing label, Samantha Jones, and Kris Ife followed, during which Wirtz formed a co-writing partnership ("Learning 2 Live With Love", MWET/Spyderbaby (2005); "One Night Stand", MWET/Anthony Rivers (2005), and the Cooking For Cannibals soundtrack album (2007).

Having become a parent in the same year, Wirtz dropped his "loose cannon" career pursuits and, under the name of Marc Peters, became a freelance session arranger/conductor in partnership with several producers, including Kim Fowley and Jimmy Bowen.

He subsequently created numerous pop, R&B and country songs that featured an array of artists as diverse as Helen Reddy, Leon Russell, Vicky Leandros, Kim Carnes, Dean Martin, and Anthony Newley.

During those years, after savings had run out and royalties had dwindled, Wirtz took on a gamut of jobs, including telemarketer, waiter, maître d', bloodstock agent, interpreter, voice-over artist, seminar leader and eventually sales manager for a Geneva merger and acquisition firm.