This is a good article. Brian mcdonald invisible ink pdf the link for more information.
In the 1970s, the anti-terrorism industry offered bullet-proof vehicles, bugging devices and security hardware, so Mardas set up companies offering these products to VIPs. Mardas had customised, but then reportedly had the changes reversed when tests demonstrated them to be useless. In 1987, Mardas was a managing director of Alcom Ltd, which specialised in electronic communications and security. He later returned to Greece. Indica Gallery in London, and later moving in with him in a flat on Bentinck Street, which was where Mardas first met Lennon.
Known at this time as Yannis Mardas, he found employment as a television repairman. Dunbar later said: “He was quite cunning in the way he pitched his thing. He knew enough to know how to wind people up and to what extent. He was a fucking TV repairman: Yannis Mardas, none of this ‘Magic Alex’ shit! Lennon later introduced the renamed John Alexis Mardas as his “new guru”, calling him “Magic Alex”.