Has there ever been a murder mystery story quite so compelling as the Lord Lucan scandal?
Even four decades after the event, people are still fascinated by this most blue-blooded of crimes. Every time that some fresh titbit of news turns up about the Lucan Scandal, it still makes the front pages of the British tabloids. And the Lucan currency is still so red-hot that ITV is screening a huge two-parter on the man tomorrow (Wednesday, December 11).
The reason this mystery continues to fascinate is not so much because of the tragic murder, but because we are still captivated by one single dominant question: what on earth happened to the Seventh Earl of Lucan, who disappeared in 1974 after the botched murder of his nanny Sandra Rivett, and who has never been seen or heard of since.
What's been interesting of late is to see how history is being rewritten. A number of Lord Lucan's supporters - including one of his daughters - have come forward to say that Lord Lucan was an innocent man. They say he did a runner because he knew he'd never get a fair trial.
And in some ways, it's admirable that Lucan's friends and family still think he's innocent, just a man who happened to be in the wrong place at the wrong time.
But unfortunately, Lord Lucan's apologists are deluding themselves. There is not only a slew of circumstantial evidence which indicates that Lucan was heavily involved with the murder, but there is also one key piece of evidence which unquestionably proves that Lord Lucan was up to his ruddy neck in the murder plot.
And though it is just about possible that Lucan may have hired someone else to commit the murder, it is far more likely that it was Lucan himself who planned to kill his wife.
First of all, the circumstantial evidence. On the night in question in November 7, 1974, Lucan had not only prepared his own alibi, arranging to meet some friends for supper at the infamous Clermont Club, but had also borrowed a car, a Ford Corsair, from his old friend Michael Stoop.
All the evidence indicates that Lucan planned to hit his estranged wife Veronica over the head with a piece of lead piping. He then intended to drive her body to the south coast, before dumping her in the Channel. The next day, he was going to be back in London, duly feigning complete ignorance as to Veronica's whereabouts. Doubtless he was going to claim that Veronica already had form for running away.
As I've said, it is just about possible that Lucan may have hired someone else to commit the murder. But it's much more likely that he acted alone.
And botched it by himself too.
Instead of going out on November 7, Sandra tragically decided to spend the night at home in Belgravia, West London, with the children and Veronica.
After watching some TV, she went down to the basement to make some tea. This was where the killer was waiting with a blunt piece of lead piping. The murder weapon was about two feet long and had some white tape around the end, to make for a better grip.
It is this piece of lead piping which came to be the smoking gun, the key evidence that linked Lucan to the murder. There is no avoiding this. For all that Lucan's friends would like to believe otherwise, there is absolutely no getting round this one very awkward fact.
The murderer had removed the light-bulb, so the kitchen was quite dark. Sandra Rivett was, like Veronica, a petite woman. In that dark basement, the two women would have seemed very similar.
Sandra Rivett was hit savagely over the head with the lead piping. All the evidence points to Lucan then trying to stuff Sandra's body into a US Mail sack before confronting Veronica on the stairs. He was covered in blood.
He also tried to hit Veronica over the head with the lead piping before she kneed him in the groin. As he went to the bathroom to wash his hands, Veronica took her chance and ran screaming down the street to the nearby Plumber's Arms.
And as for the rest... Lucan then put in a phone-call to his mother, and drove through the night in Stoop's Corsair, before stopping for a drink with an old friend, Susan Maxwell-Scott, in Sussex. By now, he had obviously been rehearsing his story.
He wrote some letters while he was with Maxwell-Scott in which he claimed to be the victim of the most terrible mix-up. He said that he'd been walking past his wife's house when he'd happened to look in through the basement windows.
He had, he claimed, witnessed Sandra being attacked and had let himself into the house to try and save her. The killer had then disappeared, leaving Lucan alone with Sandra's body and the murder weapon.
Even this far-fetched claim doesn't really stack up. I have stood outside the Countess of Lucan's house a number of times. The basement is quite a way below street level. With the lights off, it is impossible to peer inside the kitchen.
There was also no evidence whatsoever of another man at the murder scene. The only person's bloody foot-prints in the house were Lucan's.
Still - with a good lawyer, Lord Lucan might just have been able to wriggle out of all the very damning circumstantial evidence.
The one thing that they could never get away from was the murder weapon, that bent and bloodied piece of lead piping. It was left at the scene of the crime.
Lord Lucan, meanwhile, drove from Susan Maxwell-Scott's house to the Sussex coast, where he dumped Stoop's Ford Corsair in Newhaven.
The car was found a few days later. It was covered not only in Sandra Rivett's blood but also Lucan's finger-prints.
There was also something else there that Lucan had left behind. It had been left it in the boot. In his panic, Lucan had forgotten all about it.
When the police opened the boot of the car, they found a second piece of lead piping. It was about two feet long, and had white tape round the end to give it a better cry. In every way, it was practically identical to the murder weapon that was found at the scene.
Once this second murder weapon had been found, it suddenly became very, very difficult indeed for Lucan to claim that he'd just been in the wrong place at the wrong time.
If he were innocent, what possible explanation could there be for Lucan having a double murder weapon in the back of the Ford Corsair?
As soon as that second piece of lead-piping was found, Lucan must have realised that the game was up. There was certainly no possible way that he could continue to claim his innocence.
So what did he do after that? Well - who knows. But that is why the Lucan scandal is such a mystery - and why, some 39 years after the event, it still continues to fascinate.