The second in line to the British throne is to honour his close friend by picking him as one of the six godparents the newborn prince will have, in line with royal tradition.
Former Mahiki nightclub boss Guy, 31, may seem a controversial choice as he is known for his hell raising party antics and is currently facing trial over a drink drive charge - which he has pleaded not guilty to, claiming the breathalyser was faulty - but he has also been a close confidant of both Prince William and his brother Harry for many years.
A source told The Sun newspaper: ''He is thrilled to bits about being picked and everyone was congratulating him.
''He's been told informally by the prince. Guy's been a very discreet and good friend to William over the years. Those are qualities he wants to pass to George.''
Prince Harry and Duchess Catherine's sister Pippa are also expected to be asked to become godparents.
Other people said to be in the frame include James Meade, the son of an ex-Olympic equestrian champ, William's estate agent friend Thomas Van Straubenzee and the Duchess' old school friend, Alicia Fox-Pitt.
Prince George's baptism is thought to be taking place in the autumn, with a christening which will then be followed by a family party.