By Justin Parkinson
BBC News political reporter
On the afternoon of 11 May, 1812, John Bellingham, a bankrupt and embittered businessman, walked into the lobby of the Palace of Westminster.
He waited a while and, upon seeing prime minister Spencer Perceval, approached him, took out a duelling pistol and shot him through the heart.
As shocked onlookers rushed towards him, Perceval uttered the words: "I am murdered. I am murdered."
He then collapsed and died - the only UK prime minister to be assassinated.
Fast-forward 197 years, six months and one week.
Conservative MP Henry Bellingham is in the Commons, looking uncomfortable as both Labour MP Frank Dobson and Tory leader David Cameron make light-hearted remarks about his infamous ancestor.
Delivering his "loyal address" in response to the Queen's Speech, ex-minister Mr Dobson jokes that Perceval, a Tory, was the "only man in history who has been assassinated on lobby terms".
Mr Cameron replies: "When it comes to assassinating sitting prime ministers, he [John Bellingham] had a much better aim than the current foreign secretary [David Miliband]."
And so Perceval's murder continues mildly to plague the Bellinghams, a long-standing and influential political family.
Henry, the 54-year-old MP for North West Norfolk, has an ambivalent relationship with John.
Sitting in Portcullis House, Parliament's modern extension, he told the BBC: "History doesn't relate whether this appalling behaviour was a horrendous stain on the family's character or name and how the family reacted.
"All I can say is that I don't think it has held back my advancement.
"Or maybe the Tory party has felt that, such were the appalling flaws in John Bellingham's character, that I was bound to be similar!"
Humour is never away when John Bellingham is mentioned, as if time has healed all wounds.
Henry Bellingham is not sure precisely how he and Perceval's murderer are related, but there was some connection at least four generations back with John's branch of the family.
With understatement Mr Bellingham, educated at Eton and Cambridge, said: "He was always a bit of a black sheep of the family."
By any standards, John Bellingham had been through a terrible ordeal.
On a trip to Russia in 1803, he was arrested over allegations of insurance fraud, following the sinking of a ship carrying some cargo he owned.
Bellingham sought help from the British authorities, but none came.
Eventually the charges against him were dropped but, in the meantime, he had become bankrupt, meaning a further detention.
Bellingham remained in a rat-infested Russian jail for six years.
On his release he returned to the UK and urged the government to compensate him, arguing that he had been abandoned and suffered an injustice.
He wrote to the foreign secretary and frequently visited Parliament to try to persuade ministers, including Perceval, to take up his case.
Henry Bellingham said: "I think Whitehall was even more indolent in replying to letters than it is now. He was being given the run-around by government departments.
"He began appearing in the lobby. He made a habit of waiting there and lobbying different ministers. He certainly lobbied the prime minister on a number of occasions and demanded a chat with him.
"The prime minister ignored him completely and was withdrawn, and even offensive.
"It was about the fifth occasion on which he had approached him when the prime minister told him to take a running jump, so he drew the gun and shot him dead."
After John Bellingham killed Perceval, he sat down and was arrested.
The prime minister was seemingly not a popular man. As the police carriage passed through the streets, sympathetic crowds tried to help Bellingham escape.
At his trial, just four days later, he pleaded not guilty to murder.
However, the jury found Bellingham guilty after 10 minutes of deliberations.
In mitigation, Bellingham gave an eloquent defence of his actions: "Recollect that my family was ruined and myself destroyed, merely because it was Mr Perceval's pleasure that justice should not be granted; sheltering himself behind the imagined security of his station, and trampling upon law and right in the belief that no retribution could reach him."
He added: "I trust that this serious lesson will operate as a warning to all future ministers, and that they will henceforth do the thing that is right, for if the upper ranks of society are permitted to act wrong with impunity, the inferior ramifications will soon become wholly corrupted."
It was to no avail. Bellingham, 35 and a father of three, was hanged on 18 May.
Henry Bellingham, a barrister by profession, thinks his ancestor should have been found guilty of manslaughter, on the grounds of diminished responsibility, rather than murder.
He said: "The criminal justice system in those days was fairly rudimentary.
"I think he had had a nervous breakdown and probably wouldn't have been fit to plead today. I think prison in Russia was pretty horrendous. It must have knocked the stuffing out of him.
"He was incredibly bitter about his treatment. I think it's fair to say he wouldn't have hanged in today's world, even though it was a heinous offence."
The family would be forgiven for trying to forget what happened.
But Mr Bellingham said: "When I was at school, my uncle gave me a print of John Bellingham, which I always displayed, but it was stolen later.
"I've now got another print of a drawing of the murder."
'Butt of jokes'
He added: "I've always avoided raising the murder myself and I wouldn't bring it up in conversation that I'm a descendant - or a near-descendant - of a murderer of a prime minister. But I don't try to deny it.
"You could argue that the people who raised it in the House are, to some extent, making a joke about what was an appalling event. We wouldn't talk about the Kennedy murders or the killing of Benazir Bhutto in the same way.
"At what stage do these things become almost subjects for the butt of jokes and relaxed conversations that we have about them?
"Maybe for about two generations you would treat the issues with a great deal of respect."
Henry Bellingham was first elected to Parliament in 1983.
At the 1997 general election, though, his family's past resurfaced in a bizarre fashion.
North West Norfolk - regarded as a safe Tory seat - switched colours.
Labour won a majority over of 1,339, helped by 2,923 votes going to the anti-European Referendum Party, many of whose supporters might otherwise have been expected to choose the Conservatives.
The Referendum Party's candidate was one Roger Percival, described - despite the slight difference of spelling in the surname - as a direct descendant of Spencer Perceval.
The media portrayed it as a dynastic revenge of sorts.
Mr Bellingham, who regained his seat in 2001, says little of 1997: "He cost me the election. That was the nadir of my parliamentary career. It got a lot of coverage at the time.
"I think people remember the assassination as a consequence. My defeat was certainly unexpected."
The assassination of Spencer Perceval continues to crop up now and then, but rarely in the hushed tones of remembrance for the killings of more famous figures, such as Kennedy, Lincoln or Gandhi.
The Leeds band I Like Trains released a song a couple of years ago called I Am Murdered, imagining the last musings of John Bellingham as he sat in his cell, awaiting execution.
Mr Bellingham is surprised to hear of this, joking: "Maybe that was a result of what happened to me in the 1997 election."
A final irony, given John Bellingham's crime, is that Henry is a Conservative spokesman on justice.
He said: "I might be a justice minister on the 200th anniversary, in 2012. It would be a gross misuse of my position to lobby in any way for a pardon.
"I don't think he should have a pardon and I won't be requesting a pardon from David Cameron."
The MP might, however, expect a few more jokes to come his way.