Apart from a stint as marketing manager on Cabbage Patch Kids when he first graduated, Kirby is an adman through and through. He boasts 13 years' experience running high profile accounts such as Yellow Pages, Stella Artois, Heineken, Superdrug and Heinz at agencies including Abbott Mead Vickers BBDO, Lowe and Bates.
It is not merely the fact that he is jumping the industry fence that is so startling - after all, plenty of people make that leap - but his decision to do so after bitching about clients when he bowed out of the advertising industry three years ago.
"Where are the relationships built on mutual trust?" he moaned at the time, before slinging on a backpack and tripping off round the world for a year. "It's very dispiriting when clients are not interested in what we are saying. It's become like a World War One battle."
But in his new job, where he will liaise with Diageo's creative agencies over contractual issues such as performance, best practice, and pay, it is these words that may come back to haunt him the most: "Clients have to understand that the vast majority of their brand equities have been added by the skills of their agencies, which need to be better rewarded."
Kirby has no regrets about the outburst. "I felt spiritually weary with the industry. I had witnessed a change in the attitude by which clients and agencies traded with each other. But, having come back from travelling and after the dotcom boom, I think things are changing for the better. And anyway, surely someone who has strong points of view about all this is the best person to make the situation better."
Former colleagues on both the agency and client side agree he will probably do the job brilliantly. "He knows what it's like to be in the agency's shoes," says John Lowery, chairman of Lowe and Kirby's close friend. "He is intellectually at least a match for all the people he will encounter in the agencies. He's very bright and very amusing."
But Lowery also warns that Kirby's outspokenness will be something Diageo will have to get used to. "People either love him or not. He has always been true to himself, and never let the potential for upsetting people get in the way of expressing his point of view."
Thus, Kirby's biggest challenge may be learning to work as one cog within a massive corporate engine. Diageo's wheels probably grind quicker than in many large companies, but still much more laboriously than in agencies.
While part of his remit will be to advise Diageo's brand marketing directors as to which agencies to work with, his will only be one voice among many.
Lowery says: "At Lowes he had a track record for selling superb advertising to Whitbread, the question is whether he will be able to buy it. In his new role he will not be presented with individual ads himself, but he will be trying to get people within the organisation to buy good ones."
But Diageo must think he will fit in, because it hired him. "Within 30 seconds people get an idea of what he is like. It must have been looking for somebody that is going to change things," says Lowery.
Frazer Thompson, the former Stella Artois marketer and now managing director of New Wave Wines, thinks Kirby will fit the Diageo mould. "I think he will find a lot of kindred souls. Anyone who likes football trivia and playing with words will get on with him. He rightly expects those in a position of authority to be as bright as he is."
And, by convincing his new employer to let him talk to Marketing for this profile, it looks like Kirby is managing to wriggle out of the Diageo corporate straitjacket. Perhaps it is his legendary humour that has won the company over. "Oh, by common consent, I am the funniest man ever to work in advertising", he quips when this is referred to.
Thompson agrees that there is a playfulness and creativity about Kirby that is "very youngest child". "He's 41, but he thinks he's 14," he adds.
Not everyone who knows him is a fan, though. One marketing director, who preferred to remain anonymous, says: "He is deeply in love with himself. When he engages himself he is very bright, but he is a bit self-conscious."
Yet Kirby is making few assumptions about the challenge ahead. Lowery says: "For a man who doesn't show much humility, he has been going round talking to loads of people who have made the transition and asking them what it was like. He has also talked to people in big agencies about what they want from a good client."
Mark Cranmer chief executive of Starcom Motive EMEA, says Kirby is "brilliant at bringing discipline, quality and consistency to the business of communications, and great at driving people to a really focused goal. Kester Fielding, who is Adam's equivalent on media at Diageo, is one of the best media men I have met, and Adam is one of the best ad men I've ever met. Diageo has got a very clever double act going on here."
1990-1997: Board account director, Lowe Howard-Spink
1997-1999: Senior board director, Bates Dorland
2000-2001: Partner, Tempus Partners
2001-2002: Business development director, Adgistics
2002-present: Global head of advertising procurement, Diageo