London - As world leaders bury hatchets for the day and unite in paying respects to Nelson Mandela, the late South African leader may have a chance to promote peace, in death as he did in life.
Funerals of the great and the good, demanding attendance at short notice by busy and powerful leaders who rarely meet, have long been occasions for quiet diplomacy and Tuesday may be no exception - though not everyone will want to shake hands.
"It does cut through their scheduling so they can do things off the cuff," said David Owen, who as British foreign secretary in the 1970s saw several historic figures interred. "Everybody is putting in bids," he said of negotiations among diplomats for meetings on the sidelines of such global events.
US President Barack Obama may top many wish lists for a brief chat in Johannesburg, though it is unclear whom he will meet. Cuba's Raul Castro, at daggers drawn with Washington for over half a century, will be there.
But the initially announced attendance of Iran's new president Hassan Rouhani is in doubt - leaving a dramatic moment of US-Iran rapprochement unlikely.
If Obama is in demand, others are more used to cold shoulders - notably President Robert Mugabe of Zimbabwe, for whom such events offer a respite from international sanctions.
Aides to Prince Charles, representing Queen Elizabeth, will be determined to avoid a repeat of the funeral of Pope John Paul II in 2005, when the heir to the British throne had to blame "surprise" after he shook Mugabe's hand at the service.
"There are all these people who want their photograph taken with somebody who doesn't particularly want their photograph taken with them," Owen said, recalling how, at the 1978 funeral of Kenyan independence leader Jomo Kenyatta, he physically prevented Uganda's Idi Amin from shaking hands with the prince.
"He did try. And I did intercept it," Owen told Reuters, saying British officials had been in an "absolute panic" about the Ugandan dictator seizing an unwelcome photo opportunity.
Even before the event, questions of attendance have been subject to anxious diplomatic calculus - to go, or not to go?
Obama, like Mandela the first black president of his country, leads a substantial delegation reflecting high regard for Mandela in the United States. But some online commentators have used that to renew criticism of his failure to attend the funeral of former British premier Margaret Thatcher in April.
When Egypt's Hosni Mubarak visited Israel to mourn Yitzhak Rabin in 1995, some Israelis grumbled that peace would have been better served by him coming before Rabin was assassinated.
Jimmy Carter, among three former US presidents travelling with Obama to Mandela's memorial, was accused by critics of undermining US influence in the Balkans after he sent his mother to represent him at the 1980 funeral of Yugoslavia's Josip Broz Tito - a move Carter took to avoid meeting Soviet leader Leonid Brezhnev, who had just invaded Afghanistan.
When Brezhnev himself died two years later, it ushered in an extraordinary series of three Soviet state funerals in Red Square in as many years. Ronald Reagan, as US president, was moved to complain, according to biographers: "How am I supposed to get anyplace with the Russians if they keep dying on me?"
Those funerals, at the depth of the Cold War, offered vital clues to the new men following on, notably a first meeting in 1985 between Reagan's vice president, George Bush, and Mikhail Gorbachev as the younger Russian prepared historic reforms.
But it was at the previous Kremlin funeral, of Yuri Andropov in 1984, that the diplomatic power of the mourner's handshake was perhaps most memorably seen in public.
While David Owen, a physician by training, was offering his condolences to Andropov's newly named successor, Konstantin Chernenko, he detected a wheeziness in the Soviet leader's chest. He mentioned to a journalist Chernenko had emphysema - a potentially fatal lung condition common in cigarette smokers.
"It went round the world faster than I could believe," Owen recalled. "The diagnosis was correct - and it was a slight warning, I suppose, to people that he wasn't going to last that long." Gorbachev oversaw Chernenko's funeral 13 months later.
Friends, colleagues, comrades and family of Nelson
Mandela are invited to share their memories and tributes, and to light a candle
for him, on his profile at Remembered.co.za.