English Murder Not Whodunit but Where-Is-He : Mystery: After 20 years, the disappearance of Lord Lucan, suspect in woman’s death, remains unsolved.

For the British, it is the most intriguing murder mystery of the century, with enough sensational elements of class and criminality to satisfy any tabloid editor’s dream.

The story: Richard John Bingham, dashing seventh Earl of Lucan and a gambling rakehell whose great-great-grandfather ordered the Charge of the Light Brigade in the Crimean War, allegedly tries to murder his wife, the Countess, but kills the nanny instead by mistake.

After the crime in London’s most fashionable neighborhood, Belgravia, Lord Lucan flees, makes mysterious phone calls, writes mysterious letters from a friend’s country house--and then abruptly disappears from the face of the Earth.

The question remains: Is Lord Lucan, protected by rich friends, hiding out somewhere in South Africa, South America, south Australia, or the south of France, where various sightings of him have been reported?

It all happened about 20 years ago. Yet so thoroughly has the crime gripped the imagination of class-conscious Britons that the mystery has turned into something of a media gold mine: No fewer than three books, three TV documentaries and a movie have had their release dates moved forward rather than wait until the November anniversary of the crime.

“It’s a great story,” says gossip columnist Taki Theodoracopulos. “Of course, I think he’s absolutely dead. But a lot of people think he’s alive. A reader of mine in the New York Post says he’s alive and well and living in Southampton. Sees him almost daily.”

Others have changed their minds, possibly to keep the story alive. Detectives Roy Ranson and David Gerring, who when investigating the case believed that Lucan was dead, have just published separate books arguing the opposite.

The events in question took place on the night of Nov. 7, 1974.

Lord Lucan, then 39, tall and mustachioed, was called “Lucky” by his friends, all men-about-town who frequented multimillionaire John Aspinall’s Clermont Club on Berkeley Square. Lucan would often spend hours there, gambling, playing bridge, eating and drinking.

A graduate of the exclusive Eton prep school, Lucan served for a couple of years as an officer in the army’s elite and fashionable Coldstream Guards regiment before joining a London bank and the West End’s sporting set and squandering his inheritance.

In 1963, he married attractive Veronica Duncan, a typical “English rose,” and when he succeeded to his title a year later, she became a countess. They had a son and two daughters, but the marriage was rocky, and friends said he found her difficult and erratic.

They separated. He said she was mentally ill and gained temporary custody of the children. But he lost possession in a subsequent action, which cost him heavily. He complained that his wife was crazy.

Lucan’s checks began bouncing. His children’s school fees went unpaid. He borrowed money from his friend Theodoracopulos, a millionaire shipping heir, and got a large loan from another friend, financier Sir James Goldsmith. Lucan acted strange, friends said, and was drinking heavily.

On the fateful night, as police reconstruct it, Lucan went to the Clermont Club and made a fuss with the doorman--apparently to create an alibi--but he slipped back to his apartment near his wife’s house in Lower Belgrave Street.

Lucan changed into casual clothes, police said, and headed for his wife’s place--since it was the night off for the nanny, 29-year-old Sandra Rivett. Lucan allegedly entered with his key, carrying a large canvas U.S. Mail sack and a 10-inch lead pipe. His wife and children were upstairs watching television.

His wife would normally make tea in the downstairs kitchen around this time, and Lucan, lying in wait, unscrewed the light bulb, leaving the room dark.

Just after 9 p.m., a woman appeared, and Lucan struck her repeatedly with the pipe. Blood spilled everywhere. Lucan, police said, began stuffing the woman’s body into the mail bag. He planned to bundle the body into the trunk of his borrowed car and then dispose of it--later slipping back into the club.

But from the top of the stairs came the voice: “Sandra. Sandra, what’s keeping you?”

The nanny had decided not to take the night off. The wrong woman was dead.

Veronica Lucan came down the stairs, and her husband grappled with her, police said, striking her on the head. She fought back, but the struggle suddenly ended as she calmed him down and persuaded him to take her to the bathroom to wash off the blood.

Instead, she dashed out of the house and up the street to a pub called The Plumber’s Arms, bleeding and screaming: “Help me! Help me! I’ve just escaped from a murderer. He’s killed my nanny.”

When police arrived at the house, they found blood everywhere and the mail bag containing Rivett’s body.

Meanwhile, Lucan had fled. He made a call to his mother from an unknown location telling her of a “terrible accident” and asked her to get the children.

Around midnight, he turned up at the country house of friends in Sussex, a dozen miles from the English Channel, driving a car borrowed several days earlier from a London friend.

He asked for a stiff drink and told his friend Susan Maxwell-Scott that he had been walking by the home and, as he glanced in the window, saw a man attacking his wife. He entered, slipped on the blood, and the intruder ran off. His wife in the dark mistook him for the assailant. No one would believe this, though it was the truth, he said.

He drank heavily, wrote two letters to Veronica’s brother-in-law Bill Shand-Kydd--also the brother-in-law of Princess Diana’s mother--asking them to look after the children.

At 1:15 a.m., Lucan asked for sleeping pills and was given Valium. He thanked Maxwell-Scott and departed in the borrowed Ford Corsair. He was never seen again. The bloodstained Ford was found two days later at Newhaven, near the ferry terminal for France.

The next day, prominent friends met at John Aspinall’s house to discuss Lucan’s future. Some commentators suggested they acted as an “escape” committee.

In his last letter to Shand-Kydd, Lucan wrote, “I will also lie doggo for a bit, but I am only concerned for the children.”

One friend, newspaper columnist Charles Benson, believes Lucan is dead. “He must certainly have killed himself,” Benson said. “He was unhideable abroad. He would stick out like a sore thumb anywhere in the world, an Englishman from top to toe.”

Others, however, think Lucan is alive. Restaurateur Michael Proudlock, another old Etonian, speaks for many when he argues: “No body was ever found. If he had jumped off a ferry, it would eventually have surfaced. I think he got to Portugal through friends with private airplanes and then to southern Africa, where he is living now on some remote farm.”

The detectives say in their books that he is alive and in hiding--and guilty. Writer Sally Moore produced an earlier book arguing that Lucan is innocent of the crime. And one aristocratic woman who used to go out with Lucan before his marriage says flatly: “I think he’s alive and innocent. He was not a murderer. Totally out of character. I think the nanny may have been killed by her boyfriend.”

No close friend or family member--nor those of the slain nanny--has ever made a significant comment outside the court inquiry, at which they recounted the above events with slight variations.

The Countess of Lucan, now 55, is a recluse, living in the same Belgravia area. She was temporarily committed to a mental institution when she was found wandering in a dazed state several years ago, and according to those who know the family, she has been in delicate mental health for the past 20 years. She attempted suicide 12 years ago.

She allowed her sister and brother-in-law, the Shand-Kydds, to raise the children, who went to the best schools.

Today, Lucan’s son, George Bingham, 26, is a successful merchant banker who refuses to accept the title of Earl of Lucan while the mystery lingers. One daughter, Frances, 29, is a London lawyer; the other, Camilla, 23, was a brilliant classics scholar at Oxford.

“The family,” says the son, “has a policy of maintaining as dignified a silence as possible.”