The Lobby Bar of the Europa Hotel in Belfast is not the sort of place one expects to meet the Tsar. But there he is and he offers to buy me a pint of lager before I drive back to Dublin.

William Lloyd Lavery is a former schoolmaster who lives in Co Antrim. He is approaching 50 and has hardly a grey hair in his head. He is also known as Michael Gray, the pseudonym under which Victor Gollancz has published his book Blood Relative: The astonishing story of the survival of the Tsarevich written by his son.

Astonishing though his story undoubtedly is, the publishers might have applied the word "unbelievable" with greater accuracy. If someone has the temerity to claim to be the heir to the Imperial throne of Russia then he has to get his facts straight. Lavery's story, while intriguing in a "Boy's-Own-Newspaper" sort of way, happens to be full of holes. Not only that, I think it is highly offensive to the memory of many people, in Russia and elsewhere.

Our conversation in the hotel lobby in Belfast consists therefore of what the diplomats might call a "polite exchange of views" rather than the usual interview between an author and a journalist.

His tale can be summed up as follows: the Tsarevich Alexei was not killed in Yekaterinburg in 1918 and Tsar Nicholas II probably escaped too. Using the alias Nikolai Chebotarev the Tsarevich, who spent a great deal of time in Ireland, fathered a child with Princess Marina of Greece (later of Kent) and that child was William Lloyd Lavery, alias Michael Gray.

Key figures in all this, according to Lavery, are the Lievens, a family from the Baltic-German branch of the old Russian nobility. The most notable figures are

Prince Paul Lieven and his sons Prince Alexander and Prince Leonid, all of whom are now dead. Alexander Lieven, who studied at Trinity College, Dublin in the late 1930s and early 1940s, is the most important of these.

Lavery writes that only when his "surrogate" parents died and he discovered, in his "surrogate" mother's handbag, a photograph of himself as a baby with Prince Alexander Lieven and Countess Martha Apraxine did he realise he was someone special. The advance to Tsardom then began.

Strangely, this key picture did not appear in the copy of the book sent to The Irish Times by Gollancz, but it was to be found in the copies on sale at Waterstones in Belfast. (A Gollancz spokeswoman later put this down to an "inexplicable production problem".) More importantly, Prince Lieven's son Anatol, who happens to be a friend of mine, has seen it and has told me emphatically: "The man in the photograph is not my father."

I put this to Mr Lavery as we sit in the lobby of the Europa. It does not appear to disturb him in the least. Prince Alexander Lieven has been identified, he says, by a Kathleen McCarthy who knew him in Collon in Co Louth and by Alix Hill, "a cousin of Alexander Lieven who worked with him in London". The following day, Anatol Lieven tells me: "We have no relative whatsoever called Alix Hill." The Gollancz spokeswoman maintains Hill was a "distant relative" of Alexander Lieven but, more importantly, that Hill knew him well and worked with him.

A small community of Russian emigres did live in Collon in the 1930s and 1940s. Its leading member was Nikolai Couriss, who ran a school there in which the Russian language was taught. Nikolai Chebotarev, the man Lavery says was the Tsarevich, was, the book claims, a visitor at Collon and a close friend of Alexander Lieven.

Anatol Lieven says he never heard his father talk about Chebotarev. Conor Cruise O'Brien, who was a friend of Alexander Lieven, his contemporary in Trinity and who studied at the Russian school in Collon, tells me he too knew nothing of Chebotarev. "I went to Collon every week for two years. I never met him and never heard of him," he says. The book also claims the spies Philby, Burgess and McLean visited Collon. Conor Cruise O'Brien never met them: "I don't believe for a moment that they were there," he says.

Prince Alexander Lieven's father, Prince Paul, had been, according to the book, a "qualified engineer who had worked on the Omsk-Tomsk section of the Trans-Siberian railway".

I have visited Tomsk. It is not on the Trans-Siberian railway. Confronted with this, Lavery is as unperturbed as ever. "Well the Omsk section," he says. "Prince Leonid told me that."

I put it to him that Prince Paul Lieven did not work on the TransSiberian Railway at all but on the Trans-Caspian railway, he replies: "I am telling you what Prince Leonid told me."

The important, if false, inference is that Prince Paul Lieven was working on that section of the Trans-Siberian line when an attempt was made to rescue Tsar Nicholas in 1918. By all reliable accounts, he was not.

There is also a reference in the book to an attempt to trace Chebotarev's marriage in New York. Lavery writes that he contacted the Kazan Church in Sea Cliff in Long Island in New York in order to check on Chebotarev's wedding to a woman called Fanny Tate. He spoke, he said, to Alexandra Kishkovsky, a daughter of the Orthodox priest who ran the church.

By coincidence I happen to know Father Leonid Kishkovsky of the Church of Our Lady of Kazan in Sea Cliff. He has two daughters: Sonya, a journalist with the New York Times in Moscow, and Masha, who is married and lives in Paris. He has no daughter called Alexandra.

None of these contradictions seems to make any impression on Lavery. He speaks instead of a Prof Popov in St Petersburg having examined his skull, the shape of which is deemed to be imperially Russian.

Despite all indications to the contrary, Lavery continues to express the belief that he is the Tsar of all the Russias but stresses that he is not in it for the power or the money.

"I have always made it plain that I have never had these dynastic-type ambitions. I'm a sensible person. . I think identity is important. I feel I need the right to my father's name and my grandfather's name. But it rests there.

"Everybody who gets involved in this Romanov thing, either of two things always start up. One of them is: `oh they're claiming the throne of this that and the other'. Well, that throne doesn't exist," he says. "The other side of it is they always raise the Romanov money. My attitude to that is whatever existed, and I do believe money did exist, whatever existed is so well hidden and so far moved that it's impossible to recover."

Most of this may appear harmless. Imperial pretenders have always been regarded as innocent and inoffensive despite their eccentricities. But the character of one person has been seriously misrepresented in Lavery's book. An offensive paragraph reads as follows: "In 1992 Rory Peck, the brother-in-law of . . . the Earl of Caledon had been killed entering the Ostankino Television Headquarters in Moscow with Communist insurgents during the anti-Yeltsin coup." A vague connection is then made between the Pecks of Prehen House in Derry and the Russian community in Collon to which insinuations of communist collaboration have earlier been made. I met Rory Peck briefly in my time in Moscow. He was indeed killed at Ostankino. It was not in 1992 but in October 1993. He died bravely doing his duty as a TV cameraman rather than as an associate of those who attempted to take Ostankino for the communist cause.

When this is pointed out to Lavery he accepts the truth of the matter but makes no apology for the innuendo contained in his book. Instead he tells me that Gollancz employed a researcher over about eight months to check everything in his story for accuracy.

Blood Relative is presented as a true-life mystery story. To me it is a mystery that Gollancz, a reputable publishing house, should have published it as "non-fiction", if at all.

Gollancz editorial director Mike Petty says he has all sorts of evidence and sworn statements to back Gray's story. The researcher Gollancz employed to check out the author's background failed to shake him on any issue, he explains.

"It is necessarily a speculative book," Petty adds. "But if you read it carefully, the evidence stacks up in an impressive way. Part of it is theorising and you take chances with that, but where it was possible to nail things down, we have."

Blood Relative by Michael Gray is published by Victor Gollancz. Price £20 in UK.