The person credited with amassing more knowledge of the wealthy than anyone else in Britain has an interesting quirk on his CV. He cut his teeth in the information business by analysing the Irish Republican Army.
'It was my PhD thesis,' says Philip Beresford, originator of the Sunday Times Rich List and the MT Britain's Top 100 Entrepreneurs. He smiles as he hands me two door-stopping volumes from his bookcase. 'The Official IRA and Republican Clubs in Northern Ireland 1968-1974 and their Relations with Other Political and Paramilitary Groups. It took me five years and taught me many things - mainly that I'm a good collator of information.'
Meaning? 'You need discipline, a passion for the subject, a brain that does not fall asleep at critical moments and an ability to put it all into context.' And, you would think, a very thick skin, especially when you consider that Beresford's father was a major in the British Army.
Yet Beresford - born in Egypt (where his father was serving) and brought up in Britain - spent much of the 1970s, at the height of the Troubles, happily investigating Republican and Loyalist groups for his politics doctorate. 'Yes, there was quite a bit of suspicion from all sides about just what I was up to, and who for,' he smiles. 'But I am not thick-skinned really. I'm just careful.'
In recent decades that care, and a nose for opportunity, has been visible in his assiduous collating of information about the wealth accumulated in Britain. His Rich List, produced under contract for the Sunday Times and published every April, has become one of the media events of the business year, and Beresford himself an expert at winkling out even the most secretive of Britain's millionaires. It does not necessarily make you popular with everyone.
'My counterpart in Russia who compiled Forbes' first Russian Rich List was shot outside a Moscow restaurant in 2004,' he says, suddenly serious. Treading with care goes beyond just avoiding libel.
Yet standing in his bookstrewn office above his home in west London, the ever-affable Beresford seems comfortable with what he has created. Dressed in sweatshirt and baggy trousers, nursing an arthritic hip and sporting a thick grey beard, he looks like an off-duty tugboat captain with a sideline in computer studies. Screens surround his poop-deck desk, books run in low shelves beneath the garret skylights. There's even a pile of Age of Mythology computer games at a separate workstation. 'Ah, those are my younger son's,' he grins.
Beresford, 57, now runs his research operation from home - 'costs are the key' - using the mountain of accumulated data that he's amassed over the years, plus a network of subcontracted specialists and some very expensive software that allows him to break out data from Companies House and elsewhere. 'Here we go,' he mutters, tapping at a keyboard, 'company directors with income of more than £1m last year ...'
Beresford also relies on tip-offs from others and the contacts he made during the decade he spent on Fleet Street after leaving academia in the late 1970s. Back then, he worked on the business sections of the Sunday Telegraph and the Sunday Times, where he indulged his passion for trains and engineering and his love of statistics. 'I was their table man,' he grins, 'any story with a table ...'
He went on to edit MT before deciding to concentrate full-time on the Rich List, which he had launched for the Sunday Times in 1989, and to market his database. But he never lost his media sources - his wife works for the Financial Times. Happy to dispense gossip and with a smooth line in flattery built up from years of dealing with the rich and insecure, Beresford maintains good relations with many journalists. He sits at the centre of a web of information that spins in two directions, to mutual benefit.
How funny to think that his first attempt at researching a Rich List, for the Sunday Telegraph in 1983, had so horrified the aristocracy that Lord Hartwell, owner of the paper, pulled the feature before publication. The Duke of Devonshire, it transpired, had complained. Beresford is sanguine about it now. 'It was not a Telegraph thing, I was told.'
But times have changed and now Britain demands that this data be in the public domain. 'We're the best country in the world at having transparent and open recording of this kind of information,' says Beresford. 'There is an ethos of accountability and transparency, and I am a by-product of that. I've gone from being a pariah to being quite useful.'
Others are not so sure and have accused the Sunday Times Rich Lists of encouraging crime - with visions of villains studying the tables to work out who to target next. Beresford shakes his head. 'We never do anything about where anyone lives, unless it's volunteered.'
Most would just be daunted by the sheer scale of the research. Is he happy with the accuracy of his data? 'Absolutely. As with my PhD, two rules,' he says, 'never say anything stupid, and back everything up with research and footnotes.'
He acknowledges that the growth of information technology has helped him immeasurably - his first list of 200 names, researched on paper, was 'cobbled together'. Now his database has 5,000 names, and many profilees are more than willing to co-operate.
'There was a shift in 2000,' says Beresford. 'Suddenly people started ringing up asking to be included. I was saying: "Prove it, show me the figures!"'
The profile of the operation also changed when the Daily Mail tried to outbid the Sunday Times for his services in 1999. It failed, but set up rival research. 'That persuaded the Sunday Times to spend more money on production.'
The Mail eventually folded its Rich List, but not before Beresford had been threatened by one of the paper's editors: 'We'll drive you out of business, you'll be begging on the streets.'
Does he miss journalism? Beresford laughs. Not that much, you would guess. Now he can filter his database different ways for projects such as the MT Top 100 Entrepreneurs. He also has his own projects - most notably a joint venture with Reading FC chairman John Madejski called Wealth Index Ltd, which has already published one fat book on the rich. More is in the pipeline.
And can people still hide their wealth effectively from public scrutiny? Beresford gives a bristly smile. 'There are still hundreds of ways of avoiding me,' he says. But it's getting more difficult with every year.