One of Patrick Hennessey's publisher's publicists is vehement that he has no time for an interview during his whistle-stop tour of Hong Kong. Another is adamant that he does. And the handler from the financial institution that flew the best-selling author, former army officer and trainee barrister out from London for a charity fund-raiser and motivational-speaking dinner is maintaining a slightly hands-off attitude. So, once past the minders, what's The Most Popular Boy in School actually like? Popular is an understatement. The queue for a signed copy of The Junior Officers' Reading Club - the fresh-faced 27-year-old's spirited account of service in the British Army in Bosnia, Iraq and Afghanistan - following a lunchtime talk at the Foreign Correspondents' Club, stretches half way around the room. And Hennessey, dapper in a cream linen suit, Brigade of Guards tie and charity wristband, takes time to chat and swap anecdotes with each eager purchaser. Later, sporting sunglasses to ward off the glare at the Fringe Club's rooftop bar, he talks confidently and easily about the meteoric success of his book, which follows in the grand tradition of such military autobiography as Robert Graves' Goodbye to All That and Dispatches by Michael Herr. 'I didn't set out to write anything controversial, or a confessional thing,' says Hennessey, who rose to the rank of captain in the Grenadier Guards. 'I loved my time in the army, and I hope the book conveys that. There is a terrific sense of family, which is really very valuable.' It is the sense of duty and belonging that has brought him here, raising funds for Help For Heroes, a British charity that seeks to assist members of the armed forces disabled in the line of duty. 'The general level of care that's provided is pretty good, but we're trying to fund what the army calls 'nice-to-haves' - converting a car so it can be driven by someone who's lost a leg, adapting a house so it's wheelchair friendly,' says Hennessey. 'It's been very successful, and if my coming out here raises some extra money, then so much the better.' Also enjoying a distinct measure of success, Hennessey's book has hit the best-seller lists; it was recently chosen by Conservative Party leader David Cameron as one of his favourites. 'Media exposure has been very strange, I didn't expect the book to catch on,' says Hennessey. 'I suppose it's partly to do with the fact that it's current, and also because it's rare for someone as young as myself to write a book like this.' Hennessey, who is reading for the bar, says he has no regrets about leaving the army, although he clearly relished the frisson of being in action. 'When you look back at something like that, you do so with rose-tinted spectacles, and remember the best times, rather than the boring bits,' he says. 'If I had stayed on I wouldn't be in Helmand Province [in Afghanistan] now, so it just wouldn't be the same.' He is also refreshingly open about the after-effects of having served in a war zone, and witnessing friends and comrades killed and injured. 'In the regiment, we took the stigma out of counselling by making it mandatory, and taking time to talk through things,' he says. 'I saw a doctor who explained that I had had some nasty experiences at a young age with a lot of responsibility, and - quite simply - don't sweat it too much. 'However, it is hard to readjust. In 1946, nearly everybody in Britain had had some experience of the war, but nowadays it could be restricted to what they've seen on the news, so they really don't understand. 'For returning soldiers, there's a completely different set of moral imperatives. Having been praised for fighting well in Afghanistan, they have to get used to the idea that it's not acceptable to start a brawl in a pub. 'A high percentage of those tied up in the criminal justice system are ex-armed forces - so the problems are not simply in the war zone, but at home too.' It's the justice system that has lured Hennessey away from a life in uniform, and he is due to start his pupilage late next year. 'The training is insanely competitive, and while there are lots of texts to study, there's also the practical side,' he says. 'We role-play on camera - it's very cringey watching yourself on DVD afterwards, I can't stand the sight of my own voice [sic]. 'It's also an expensive course, at least GBP30,000 [HK$383,575], which I couldn't afford but for the success of the book. At this stage, I'm planning to go into conflict and international humanitarian law, but that may change - it's always best to stay flexible.'