He established a rights management organisation called MainMan and helped launch the careers of Iggy Pop, Mick Ronson, Mott the Hoople, Dana Gillespie, Lou Reed, Luther Vandross and John Cougar Mellencamp.

One of four children born to Edward and Lily Defries, the family had a second-hand and antique business close to Shepherd's Bush Market.

While he was a legal executive at the lawfirm of Martin Boston & Co.[9][7] in Wigmore Street, London he advised Mickie Most in a dispute involving The Animals in 1964.

Through Silverstein, Defries was approached by other photographers such as Brian Duffy, David Bailey, Terence Donovan[9] and Antony Armstrong-Jones.

[15] Defries and Myers worked with songwriters, composers, performers and producers, including Mike Leander, Geoff Stephens, Peter Eden, Barry Mason, Roger Cook, Mike D'abo, Donovan, Roger Greenaway, Lionel Bart, Neville Nixon,[16] Ossie Byrne and Tony Macaulay.

[17] Defries was responsible for proposing and overseeing legal proceedings for Tony Macaulay in what became a landmark case against his publishers, Schroeder Music, to recover his copyrights.

GEM's first release, on Bell Records, was "Love Grows (Where my Rosemary Goes)" performed by Edison Lighthouse, and written and produced by Tony Macaulay.

[21][22] In 1970, Olav Wyper, the head of Philips UK, recommended Defries to Bowie who was dissatisfied with his manager Ken Pitt and needed help.

[26] In 1971, Defries had decided that breaking Bowie in the US would require a permanent corporate presence and suggested to Myers that they open offices in New York.

By that time, GEM had established a significant position in the UK industry and Myers was uncomfortable about risking that base in a new US venture.

They signed an agreement where Defries would take David Bowie, Iggy Pop, Mott the Hoople, Dana Gillespie and Mick Ronson in return for a financial settlement.

[29][1][11] A key part of Defries’ strategy with MainMan was to control the creative process of Bowie's next album, Hunky Dory, by funding it independently, before approaching RCA.

[31] This gave Bowie creative freedom, without being forced to fit into any traditional record company genres[31] and co-ownership of his music copyrights.

With Bowie on the brink of stardom (Ziggy Stardust hit #5 and Hunky Dory #3 on the UK charts and hundreds of Ziggy clones attended his concerts),[35][36] Defries informed his staff "As far as RCA in America are concerned, the young man with red hair sitting at the end of this table is the biggest thing to come out of England since the Beatles.

[37] Defries instructed Tony Zanetta to set up the MainMan office in an Upper East Side New York apartment and he employed a cavalcade of exotic characters.

[38] The first North American concert date was September 22, in Cleveland for an audience of three thousand and the tour ended December 2 at Tower Theatre, Pennsylvania.

After that first concert Defries had promised they would come back to play Cleveland in a bigger venue holding ten thousand people and that is exactly what they did.

[41] Defries saw Mick Ronson as an extraordinary musical talent and believed he could have a solo career and together they devised a course to stardom, starting with concerts at the Rainbow Theatre.

[45] Ronson's production and arrangements of notable albums such as Hunky Dory, Ziggy Stardust and Aladdin Sane showed his skills in the studio and in live playing.

[61][62] "In the early days," Bowie said in 2003, "all the greats like Mick Jagger and John Lennon were forever telling me the same thing: don't have anything to do with managers.

[66][67] In 2005 Defries founded Matter Inc, a Caltech/Stanford startup for plasmonic research and development with scientists from Stanford, California Institute of Technology and New York University to work on materials science, nanophotonics and energy related projects.