WHAT IS one to make of the death of James Rusbridger, a lonely communicator who sought media attention in abnormal measure, writing up to a dozen letters a week to newspaper editors scourging the intelligence services and political egos, plus some challenging books; who, running out of steam, and cash, ended up hanged, clad in a black oilskin coat and wearing a gas mask?

'I like the sound of my own voice,' he confessed to me two years ago. Last week, it was cut off. The final sound he heard was of his own breath labouring in the Second World War gas mask. Was it suicide? An accident? Murder?

Devon and Cornwall police are still examining photographs, documents and video cassettes removed from Mr Rusbridger's rented cottage near Bodmin. But in advance of the post-mortem results, which will provide at least some of the answers, investigators are not treating the death of this exposer of state secrets as suspicious.

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Mr Rusbridger also volunteered, in that 1992 conversation, that he was 'doing a book on pornography', a subject that, until he mentioned it, seemed beyond his range of curiosity. The police and ambulance people who removed his body from the cottage would have noticed soft-porn pictures, mainly of black women, pinned up in discreet places.

The circumstances of Mr Rusbridger's death are as bizarre and mysterious as the recent fate of the Tory MP Stephen Milligan. The latter's colleagues angrily denounced disclosures about his corpse (naked but for women's stockings, bag on head, orange in mouth, flex around throat). They seem unexercised by the equally prompt - and weird - disclosures concerning Mr Rusbridger's (the oilskins, the gasmask - and a rope connecting neck and ankles to a series of pulleys). Why did the man-in-a- mask in Bodmin rate a less anxious response than the man-in- a-bag in Hammersmith?

That, at least, may be simply answered. Scorned by a disenchanted press, the parliamentarians were given, through the Milligan affair, a chance to rally round one of their own and attack their media persecutors (journalists might have bribed policemen, it was suggested). The iconoclastic Mr Rusbridger, however, was less deserving of their concern.

James Rusbridger might have revelled in the disparity, could he have foreseen it. What he did foresee was a persistent burden of debt, failing health, eviction from the cottage, and, above all, marginalisation in his chosen arena, where conspiracy cohabits with incompetence.

His literary agent, Andrew Lownie, who saw him in December, says: 'He had a heart attack last year, and wouldn't talk about it. But one knew he was down. He was frustrated about the poor distribution of his books. He was an expert defence witness in the recent trial of the KGB operative Michael Smith. It took him away from his work for longer than he'd expected. He also felt the defence lawyers had not treated him very well in the way he'd been compensated. He took a complaint to the Law Society. All this put him off his stride.'

His stride frequently took him along the cliffs of Cornwall after a prolonged session at his word processor or fax machine. Mostly, his cogent letters had something important, if not disturbing, to impart.

Last Sunday, he posted his last letter to the Independent on Sunday. Addressed to Leonard Doyle, of our foreign staff, it was a typical testament to his expertise in espionage techniques: 'As a small tailpiece to your interesting article today about the National Security Agency, it is worth mentioning that, ever since the end of the war, both the NSA and GCHQ have continually trawled patent applications around the world to see if any new encryption devices are being developed.'

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In the United States and Britain, he explained, any patent considered to be detrimental to 'national security' can be impounded by the government. 'When the new Global System Mobile (GSM) cellular telephone technology was first inspected . . . engineers from MI5 and GCHQ found the A5 digital scrambling code GSM was to use (which is similar to the Army's Ptarmigan) was too secure and would make it impossible for them to tap calls. As a result, BT insisted the manufacturers downgrade security to the A5X digital system, thus enabling MI5 and GCHQ to continue eavesdropping . . .'

Mr Rusbridger's 2,000-odd letters to editors suggest a man bent on recognition as a force to be reckoned with. The death of his father, a colonel in the Duke of Wellington's Regiment, stopped him going into the Army (he became a sugar dealer instead). His older brother Charles, now also dead, had been in Naval Intelligence. His cousin was Peter Wright, the ex-MI5 officer whose memoir, Spycatcher, got up Margaret Thatcher's nose, lodging there despite injunctions to have it removed.

Mr Rusbridger, on the other hand, was destined for the intelligence fringes - in the 1960s as an MI6 and CIA courier, later as self-appointed watchdog until his death at 65.

The past year's output claimed that 'corruption, fraud and errors' in the DSS was more than matched by the pounds 1.2bn 'squandered' by the Ministry of Defence (Sunday Telegraph); lashed the intelligence agencies 'who, like drunken sailors, have propped up each other's extravagant lifestyles' (Telegraph); revealed that the Home Secretary never asks to see the complete files on persons he allows to be bugged (Independent on Sunday); corrected an article on the Russian spy George Blake (Sunday Times); rubbished the Home Secretary's claim that MI5 is accountable, through him, to parliament (Times), and delivered acerbic comments on a wide range of other matters, from expenditure on the Royals to Foreign Office sanitising of intelligence reports for politicians.

I knew he had almost completed a book on the sinking of the Lusitania, which might have been as successful as his The Intelligence Game and (with Eric Nave) Betrayal at Pearl Harbor. But he never referred further to the porno book. On looking back over his published letters, however, I came across one - in the Independent last April - about an advertisement for the Vauxhall Corsa. 'Parts of it are pure pornographic fetishism. . . . one of the most popular forms of sado-masochistic fantasy is men being dominated by coloured women dressed in leather or rubber.'

And so to the black pin-ups. 'Friends', popping up anonymously last week, recalled for the Press Association that the fire brigade once rescued Mr Rusbridger after he became stuck in a garden shed. His clothing on that occasion was 'bizarre', and the gas mask was again in evidence. There were whispers about a past 'mental condition'.

Whatever the truth, James Rusbridger's whistle-blowing must have created enemies. Experienced, independent- minded journalists insist he was 'extremely accurate on security matters' and 'showed many government people to be liars'. Might someone have wished him dead?

Last week, Mr Rusbridger sent bundles of research material on the pornography industry to a television station and a newspaper. The documents were said to have named certain members of the Royal circle with 'exotic sexual appetites'. This material must form a tiny section of voluminous Rusbridger files painstakingly assembled over the years. Who will claim them? What embarrassments do they hold? Is there a will? An explanation?

Among other puzzles is how he came to run out of money, having earned substantial royalties (he mentioned advances of pounds 50,000 on two of his books). Behind with his rent by pounds 6,000, he was about to be turned out of his cottage.

His phone and fax had been cut off, for non-payment of bills. This may have been enough for suicide. But in that case, why did he not leave a suicide note?

A year ago, Mr Rusbridger penned a short outburst to the editor of the Independent. 'One of our greatest codebreakers in the last war, Alan Turing, was a homosexual,' he wrote, 'but the police did not concern themselves about this until after the war when, it has been alleged, their harassment led to his suicide.'

(Photograph omitted)