NOTHING fascinates like a good murder. Public interest in a grisly demise is insatiable and literature, cinema, television and news media all respond accordingly.

All the better if the murder is real, but bears the hallmarks of fiction — larger-than-life characters, doomed love affairs; a status, class, or rank well above the common low-life associated with such ghastly goings-on, and a chief suspect who has vanished into thin air.

In 1974, one such murder met all the criteria and it continues to intrigue today. Richard John Bingham, 7th Earl of Lucan, the aristocrat with the movie-star looks, Eton education and calamitous gambling habit, allegedly battered his children’s nanny to death with a length of lead piping, on a November night.

He had apparently mistaken 29-year-old Sandra Rivett for his estranged wife, Veronica, whom he also allegedly attacked and injured, when she came on the bloody scene in the basement of their former marital home in elegant Belgravia, one of London’s most enviable addresses.

He then fled, making contact with several acquaintances over the next few hours, before performing one of the greatest disappearing acts in history.

It took years to officially settle matters. At Rivett’s inquest, the jury found she had been murdered by Lord Lucan.

Then, in 1999, 25 years after Lucan’s disappearance, the courts declared him legally dead, presumed by suicide, his car having been found by the coast. But for his family and friends, and for countless murder-mystery aficionados, there is no certainty.

Their doubts have been kept alive by claimed sightings of the fugitive, everywhere from Africa to Australia, as well as by flaws in the police investigation and the belief that the man they knew was incapable of murder.

The unanswered questions have inspired countless articles, at least a dozen books, numerous TV dramas, documentaries, one dreadful pop record, a cameo in Christy Moore’s song, ‘Lisdoonvarna’, a soft toy in dubious taste (called the Lord Lucan Toucan) and The Lord Lucan pub, in west Dublin ( the first Earl of Lucan was born locally, though the family estate was in Mayo).

With last year’s 40th anniversary, rehashed output was inevitable, but the latest book to tackle the subject, A Different Class of Murder, by Laura Thompson, is also a different class of examination.

For Thompson, the attraction to the story of what happened on that winter night in Belgravia has its origins in the 16th century, from which she traces a long line of murders by men of title, who availed of unofficial aristocratic immunity to escape the consequences.

The shake-up of Britain in the social revolution of the 1960s swept away deference to the lords and ladies of privilege, but it didn’t dim the fascination and it fuelled a prurient desire to see the upper classes get their comeuppance.

“Indeed,” Thompson writess, “one of the most striking things about the aftermath of Sandra Rivett’s murder was that, in the court of public opinion, an earl was the worst thing that a murder suspect could be.”

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Events took on a theatrical air and the killing was dubbed the ‘Upstairs Downstairs murder’. This was a reference to the popular TV period drama — the Downton Abbey of the time — that followed the lives of those who dwelled and toiled in a fine townhouse in none other than Belgravia.

But Thompson doesn’t settle for casting Lucan in the role of stage villain and she offers a detailed account of his early life, education, short-lived banking career, professional gambling and marriage to Veronica.

Veronica’s sister, Christina, was married to Bill Shand Kydd, and that couple would later assume responsibility for the Lucans’ three children, who remain estranged from their mother to this day.

The picture of Lucan that emerges is of a naive man driven to desperation, not only by debt, but by devotion to his children, whose welfare he feared for when his marriage to Veronica broke down.

He made strenuous, but unsuccessful, efforts to win custody of them — such efforts were almost unheard of in the 1970s, when child-rearing was still considered women’s work.

All the while, he was living a nocturnal existence in the surreal surroundings of the Clermont Club, where film stars and playboys made and lost fortunes with dizzying repetition.

Veronica, too, comes under Thompson’s scrutiny. Her unstable mental health, spendthrift ways and inability to hold on to nannies pointing to the fact that gambling was not the only problem the marriage faced.

But it is not an unsympathetic view of the now-76-year-old, who still lives just minutes from her old home, and whose website claims there was a deliberate campaign to have her falsely declared mentally ill.

Rivett, so often overlooked in retellings of the Lord Lucan story, also receives close attention.

The mother of two children (her son was raised to belive he was her brother; the other child was given up for adoption), she had overcome personal difficulties to become a nanny and was a stable influence on life in the Lucan household.

Thompson becomes most forensic in analysing the murder, including police failures to preserve the crime scene, discrepancies between Veronica’s evidence of where the attacks on herself and Sandra took place, and the location of their respective blood spatters.

Thompson points out that the disappearance of the presumed murder weapon from police custody meant it was denied future advances in DNA sampling, and she ponders the troubling fact that little blood was found in the bedroom where Veronica has always claimed her husband brought her while he tried to work out what to do about his dreadful ‘mistake’ lying dead downstairs.

So was he really the killer and, if so, was Sandra a mistake or his intended victim?

“Only two people know what happened on the night of 7-8 November 1974,” Thompson writes, “and only one of those people has been heard.” Thompson runs through various alternative theories to the standard ‘crime of passion’ conclusion the police settled on.

Rivett could have been the intended victim, as her calming influence on Veronica did not help Lucan’s custody case. Or, perhaps it was a botched burglary, as the house held substantial valuables and what Lucan needed more than anything was money.

Or, there’s Thompson’s own preferred version, which involves a hitman, a contract to kill, a last-minute change of heart and a very bungled outcome.

That might sound like the stuff of crime novels, but then there’s little in the true-life story of Lord Lucan that doesn’t sound like it sprouted from a fertile imagination. As for the big question of whether Lucan (who would now be 80) is still alive, Thompson concedes the evidence to the contrary is overwhelming. But not conclusive.

The fascination factor isn’t going to fade any time soon.

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