It may be pushing it to compare Philip Bobbitt with Indiana Jones, on the basis that a constitutional lawyer will never have the exotic and uncommercial appeal of an archaeologist adventurer, even if he does look remarkably similar. Then again, a profile of him in the New York Observer called him the James Bond of the Columbia Law School, which also suggests impossible glamour.

But you can see why his students and reviewers come over star-struck. He’s a courteous, urbane, well-connected (nephew of Lyndon B. Johnson) literary academic, adviser of presidents but way above the party fray, possibly the last Wasp standing in the academic elite, certainly the last cigar-smoker, a Big Name in western foreign policy circles by virtue of his last two books, The Shield of Achilles and Terror and Consent. He’s now 63. There was general fascination with his second marriage — at the Supreme Court, if you please — a couple of years ago to Maya, a Turkish law student, a formidable young polyglot who showjumps for Turkey and engages in deep sea diving. His books on US foreign policy are admired by Tony Blair and Rowan Williams. His latest, a rethink of Machiavelli, has a glowing blurb (‘extraordinary intellectual endeavour… may become a new standard interpretation’) from Henry Kissinger.

In fact he has a curiously old-fashioned charm — he’s the sort of man who will, quite disarmingly, ask you for your opinion about things and is tactile in a non-problematic sort of way. And apparently he can blow smoke rings.

We met in Albany, the Piccadilly roost where he has the nicest flat, with, unexpectedly, a little rocking horse in the hall. ‘We had a first birthday party yesterday,’ says the Prof of Pasha (a nice Ottoman touch), his first child. Then Pasha himself unexpectedly turns up, a sweet round-faced boy. ‘It’s been a very happy time,’ says Bobbit of his marriage.

But back to the book — The Garments of Court and Palace: Machiavelli and the World that he Made (and the day an academic produces a book without a catchy surtitle is when history really will be made), written to raise $25,000 for a charity which asked him for that sum. It was meant to be part of the publisher’s series of Ten Books that Shook the World, only he took so long (six years) to write it, it turned into Nine Books that Shook the World instead. The book is a take on Machiavelli’s Prince, the one that gave us the dictum (except it didn’t in so many words) that the end justifies the means. Prof Bobbit points out that the original title of the work is the less snappy On Principalities, and should be read alongside his other work, Discourses on Livy, as part of an agenda for government, or what Prof Bobbitt calls The State.

There have been any number of Machiavelli: Not As Bad As You Thought books, but Prof Bobbitt’s USP is that his take is that of a constitutional lawyer. The Prince, he says, is ‘obviously a constitutional treatise… it’s so obviously about the state’. So it’s not one of those advice books for princes, nor a satire. Machiavelli, in fact, was, as Prof Bobbitt quotes others saying, ‘the spiritual forefather of the US constitution’. Well, sort of. At the end of The Prince Machiavelli does call for a ruler to bring about a new Italian state, but he didn’t call it a republic. The Prof is unabashed; I should read Machiavelli’s constitutions for Florence, he says, where Machiavelli points out that the dynastic element would only last for a limited time.

Machiavelli is, of course, a byword for underhand dealings and cynical realpolitik. He’s entered the language as an adjective, and not in a good way. Professor Bobbitt however, puts up a spirited case for the defence. ‘Of course the end justifies the means,’ he says. ‘What else are means for? But the question is, what ends and what means? The end of supporting a totalitarian state is a very different end than supporting a democratic republic.’ Machiavelli certainly justified murder and oathbreaking by rulers but only for the common good, in the interests of the state. ‘Remember, he does savagely attack unnecessary cruelty,’ says the Prof. ‘In his personal life he was seriously ethical at a time when everyone else was stealing. He’s more ethical than most of his contemporaries. But when you are responsible for a state, you are obliged to prefer the interests of the people on whose account you are acting. It’s the duty of consequentialism.’

So what are the lessons of Machiavelli? He’s reluctant to project Machiavelli into the present in a Jane Austen Guide to Dating sort of way. But ‘if I had to come up with just one thing I would say that Machiavelli emphasises that if you depose a leader you must be wary of the insurgents which are your allies. You have to reach out to groups that have been removed from power. They’ll be grateful if you protect them.’ And yes: ‘Machiavelli wouldn’t have disbanded Iraq’s police and army and would have been more effective.’

Which modern statesman might be called Machiavellian? He pauses. ‘I hate to say someone like President Johnson was Machiavellian,’ he says. ‘One hesitates to bestow the compliment. But he had the ideal of working for the common good. He said something that could have been right out of Machiavelli: ‘Take no small risk.’ If you have some great project, like building a state, risk life and torture, but don’t do something small and stupid.’ (For the record, uncle and nephew were friends. ‘I liked him very much. He and I had friction for a time… I tried to show that I was independent of him, and he was a very generous man and that annoyed him.’)

In fact the lessons he draws from Machiavelli are not what you might think: the necessity of dialogue between the governors and the governed, and for rulers not to act on partisan lines but in the interests of all. ‘He praises the tumults of Rome and contrasts that with the violence of factions in Florence. I conclude that there’s a very important role for public agitation if it’s not violent. He would have had sympathy with demonstrators in Cairo and Istanbul.’ As for leaders who are good at engaging with the opposition, he mentions President Obama and Nelson Mandela. ‘He was sensitive to the views of the Afrikaaners and learned Afrikaans,’ he said. ‘As for Obama, he’s good at listening.’

Machiavelli also takes a dim view of liberality in a state that can’t afford it. What would he have made of David Cameron increasing spending on overseas aid when he’s trying to cut the deficit? The Prof nods vigorously. ‘Yes, a show of liberality… it ends up that the cost of funds go up and you impose more taxes on your own people. He was against that.’

The need for communication between rulers and governed extends to all areas of politics, he thinks; even gay marriage. He himself supports the recent Supreme Court judgment. ‘Personally, I support gay marriage,’ he says. ‘I’ve gone around on this. I think it’s the right thing to do but I think it’s best when it’s not imposed by a sophisticated elite but a consequence of persuasion of the public. I would distinguish between the legal consequence of marriage and the spiritual and religious side. Two different spheres… it sounds Machiavellian.’

He is himself a member of a persecuted minority in American life, namely smokers; but he weathers stigma with good grace. ‘I can’t smoke in any of my clubs,’ he says, ‘because Mayor Bloomberg won’t let me. I can’t smoke in a public park. There’s a terrace in my apartment where I sit outside in the snow.’ Outrageous, I murmur. ‘You know,’ he says, ‘I hate to offend people.’

He loves Britain. ‘It’s a puzzle,’ he says, ‘that British people have such insight into my work.’ In the US you often hear complaints that my books are too long. The British are more patient.’ Actually, at 164 pages, excluding acknowledgements, his latest weighs in as a nice short read. Just like The Prince, then.