On leaving drama school in London at the age of 15, Greg joined the Argyle Theatre Touring Company and then took a job as a runner to impresario, Bernard Delfont. Subsequently, he became an agent with MCA until its enforced closure in 1964. Shortly afterwards he established his own talent agency and assembled a respectable client list of producers, directors and writers, amongst whom was Norman Cohen and together they made the documentaries,"Brendan Behan's Dublin"
and "The London Nobody Knows".

Their success enabled Greg and Norman to acquire the film rights to the BBC TV series "Dad's Army" for Columbia Pictures. This was quickly followed by the film of Spike Milligan's novel "Adolf Hitler - My Part in His Downfall" for United Artists.

His return to Columbia Pictures led to the hugely successful "Confessions of …." series, the first in 1974 "Confessions of a Window Cleaner" grossed a higher sum per dollar spent than any other Columbia film in the non-US markets and gained entry into the Guinness Film Book of Records.

At the same time he also produced "Never Too Young to Rock" for GTO and the award-winning documentary "The Importance of Being Dublin" in 1975, and for Warner Brothers, arising from his association with Leslie Thomas, the successful "Stand Up Virgin Soldiers" in 1976/77.

Greg then persuaded the Rank Organisation to allow him to recreate "The Thirty Nine Steps" (starring Robert Powell, John Mills and David Warner) from Buchan's original book rather than as a remake of the famous Hitchcock version. In 1979 he turned his attention to television, both film and series. This led to the making of the series "Tropic of Ruislip", for ATV's 1979-80 season. In 1980 came the TV movie "The Shillingbury Blowers" starring Trevor Howard and leading to the popular series "Shillingbury Tales" in 1981/82; then another Leslie Thomas creation "Dangerous Davies - The Last Detective", both for ITC.

The early '80s saw Greg making the independently financed movie "Funny Money", as well as "The Boys in Blue" for the Rank Organisation, and the TV series "Cuffy" for the 1982/83 season. He has been mainly involved in TV production since then, with a 12 x 1 hour series for Euston Films "Prospects" (1984/85), and two series of the Channel 4 sitcom
"Rude Health".

"Great Expectations" followed in 1988/89, a 3 x 2 hour mini-series for The Disney Channel/Primetime/HTV, (starring Anthony Hopkins, Jean Simmons, Ray McAnally and John Rhys Davies) which received two ACE awards
and four EMMY nominations.

Greg co-produced "Buddy - The Buddy Holly Story" , with Laurie Mansfield and Paul Elliott, opening at the Victoria Palace Theatre, London in 1989 and moving to the Strand Theatre in 1995. The stage production proved a major hit both in London’s Theatreland and on tour in the UK and World Wide. “Buddy” has been nominated for many international awards including two English Laurence Olivier Awards, one US Tony Award and six Canadian Dora Mavor Moore Awards. After 13 successful years, it left the West End for new UK and European tours. It will be back!!”

During 1987 to '89, Greg chaired the British Cannes Action Committee and the British Pavilion at the Cannes Film Festival
(a Government sponsored and all industry project, emanating from the British Film Year). In 1989-90, Greg produced Trevor Nunn's highly acclaimed production of "Othello" for BBC and Primetime (starring Sir Ian McKellan and Willard White), which received two BAFTA nominations and in 1992 Trevor and Greg joined forces again to make the world television production of Gershwin's operatic masterpiece "Porgy and Bess" for BBC, American Playhouse and Primetime based on Nunn's renowned Glynbourne and Royal Opera House production.
Following the production of "The Old Curiosity Shop" as a mini-series for Disney and Hallmark starring Sir Peter Ustinov, Tom Courtney, and filmed in Ireland.

Greg and Trevor Nunn jointly formed Circus Films Limited which, in 1995/96 produced, "Twelfth Night" for NewLine.

Also in 1995, and continuing his association with Laurie Mansfield and Paul Elliott, they brought "Jolson" to the Victoria Palace, London with Brian Conley playing the title role. The show was awarded the Laurence Olivier Award of "Best Musical 1996". In the Spring of 1996, Greg produced Neil Simon's "London Suite" for RHI/Hallmark Entertainment Inc., to appear initially on NBC, and which was filmed at the Grosvenor House hotel and Shepperton Studios.
In 1998 Greg, as Producer, set up a production studio site in the Luggala Valley in the Wicklow Mountains of Ireland to film George Orwell's "Animal Farm" for TNT/Hallmark, using both live animals and animatronic doubles and with post production in London - and within weeks of the completion of this shoot.

"David Copperfield", again for TNT/Hallmark, commenced shooting in Dublin, with Greg as Co-Producer, finishing in March 1999.

During this period, he and Laurie Mansfield also Co-Produced "Agnes Brown" with Jim Sheridan and Morgan O'Sullivan for October Films / Hells Kitchen.

In the London theatre, Greg and Laurie Mansfield, with Chris Davis, Chris Marino and Effective Productions, brought "Animal Crackers", the acclaimed Royal Exchange Theatre production the Marx Brothers' comedy classic to the West End for a limited tour. In July 1999, Greg, Laurie Mansfield, Jim Davidson and Robin Clark launched "Great Balls of Fire", the Jerry Lee Lewis story, in Plymouth, Birmingham and at the Cambridge Theatre, London. Opening in February 2003, Greg was a co-producer of the musical “ZIPP!” at the Duchess Theatre, following an award winning season at the 2002 Edinburgh Festival.

He was married to the actress Lynda Bellingham.