The bicentenary of his assassination on 11 May 1812, in the lobby of the House of Commons, is being marked by national institutions and local churches

Until the posters announcing a bicentenary memorial service and concert started to appear, few people even in Charlton – once a village on a hill overlooking the Thames, now swamped in the suburban sprawl and traffic east of Greenwich – knew that a man with a unique place in British history was buried in their church.

Before 11 May 1812, Spencer Perceval might have hoped history would remember him as a brilliant legal mind, a shrewd politician who became prime minister at a tricky time, when the Tory George III was mad and the Whig Prince Regent recklessly extravagant, or even as the co-star of a surprisingly romantic runaway marriage and father of 12 children.

But 11 May changed all that. As Perceval slipped into the lobby of the House of Commons through a side door, John Bellingham, a businessman with a festering grudge against the government, stepped forward and shot him through the heart at point-blank range. Perceval just had time to murmur "Oh, my God", or "Murder" – as shown in documents the National Archives has just released online to mark the bicentenary, the horrified witnesses had confused memories – before he fell, the first and only assassinated British prime minister.

"He was a good man, a truly religious man, and he deserves to be remembered," the rector of St Luke's, Erica Wooff, said of the memorial service that Perceval's descendant Lord Gough will attend, and the concert of music of his time. "We didn't want to celebrate a murder; we want to celebrate his life."

Within a week, Bellingham had been tried, refused leave to plead insanity and found guilty, executed by public hanging at Newgate and handed over to the anatomists to be dissected. Perceval, meanwhile, was brought in an impressive funeral procession from Downing Street to Charlton, to be buried in a family vault at St Luke's.

The last man to have seen his face, however, is the retired sacristan of the church, Vic Skinner, nearly two centuries later. In the 1980s, Lord Gough was concerned that damp – the church is in urgent need of expensive restoration work – subsidence and the constant rumble of passing heavy traffic might be disturbing the bones of his ancestors. So the flag stones were taken up and Skinner, who has spent most of his life working for St Luke's, descended nervously by ladder into the vault, just below Perceval's wall memorial, with a portrait bust by the celebrated sculptor Sir Francis Chantrey.

He found that the coffins were indeed slipping and in danger of falling from their marble shelves, and that the lead lid of Perceval's was ajar. Skinner could not resist looking in, and was astounded.

"I've seen the sculpture of him almost every day of my life, and I would have recognised him immediately: his body was absolutely perfect. He was buried in a black suit, and that was showing the marks of time, but his face looked as if he'd been down there a week, not 200 years. He looked very peaceful."

St Luke's is opposite Charlton House, now a public park, library and council offices, where Perceval was brought up in grandeur but not wealth: he was the seventh of 12 children, and the second son of the second marriage of the Irish peer Lord Egmont, who died when he was eight. A pale and modest man, he had to work for his living, and eloped because his prospective father-in-law turned him down flat.

When he died, Perceval is said to have had £106 5s and a penny in his bank account. A contemporary MP, Henry Grattan, described him admiringly as: "Not a ship-of-the line, but he carries many guns, is tight built, and is out in all weathers."

At his trial, Bellingham, who blamed the government for not freeing him from imprisonment in Russia, apologised to the Perceval family, and explained that he would have preferred to shoot the British ambassador to St Petersburg.

All of Perceval's portraits, including one in the Palace of Westminster, were made from his death mask, which has been on display at another London church, All Saints in Ealing, built in his memory in 1905 on the site of his last family home. All Saints is also holding a service and concert to commemorate the assassination.

The marble bust at St Luke's has a faint, enigmatic smile. Gwen Zammit, leader of the group of parishioners who have organised the commemoration, has tenderly dusted it for the event. "We're very fond of him, he's one of us and we're honoured to have him."

• This article was amended on Friday 11 May 2002. The last man to have seen Spencer Perceval's face was Vic Skinner, not Stringer as we said originally. This has been corrected.