For historians in South Africa, it has become a holy grail. The pistol given to the young militant Nelson Mandela, and hidden by him underground half a century ago, has gone down in legend as the first weapon of the war against apartheid.

But an attempt to reunite the 92-year-old with the artefact has collapsed into a bitter dispute between museum officials and the owner of a house where it is thought to be buried.

The Liliesleaf Trust, which preserves the former headquarters of the armed wing of the African National Congress (ANC) -- Umkhonto we Sizwe, meaning "Spear of the Nation" -- said it had been denied access to the neighbouring property because of its owner's "belligerent and selfish stance".

But Al Leenstra, the homeowner, said through his lawyer that he has offered to sell it at a reasonable price, and accused the trust of twisting the facts to manipulate public emotion.

While the two parties continue to wrangle, the hopes of returning the gun -- estimated to be worth R22-million (£1,9-million) -- to South Africa's first democratic president, or to the ANC in time for its centenary next year, appear to be dwindling.

The semi-automatic Makarov pistol was presented to Mandela in 1962, reportedly on the instructions of emperor Haile Selassie, by the colonel in charge of his military and political training in Ethiopia.

Mandela then returned to Liliesleaf farm, the secret base of the ANC's military wing in Rivonia, Johannesburg, where he wore blue overalls to pose as a caretaker under the alias David Motsamayi.

'Held to ransom'
In July 1962, Mandela took the precaution of wrapping the gun in foil and an army uniform and burying it under a tin plate along with 200 rounds of ammunition. He was arrested soon after and charged in what became known as Rivonia Trial in 1963. In the decades that followed a number of new buildings appeared at Liliesleaf, including the house above the pistol's apparent hiding place.

Allister Sparks, a veteran journalist, recalled a visit to Liliesleaf with Mandela years after his release. "He was reminiscing about all the things that had gone on while he was there," he said. "He said to the house maid, 'Where's the kitchen? I buried some weapons here 20 paces from the kitchen.'

"We went to the kitchen and he stepped out his paces but by the time he got to 10 he hit the garden wall. So it was over in the neighbour's property — Anyway, we never found it and poor Nick Wolpe has been digging ever since."

Wolpe, chief executive of the Liliesleaf Trust, was asked by Mandela in 2003: "Have you found my gun?" He is eager to search the neighbouring property, but says he is now "being held to ransom" by an asking price of R3-million (£265 000) to buy it. Wolpe said the search "has been brought to an abrupt halt by the unreasonable behaviour of the owner of the property" where the gun is possibly buried.

"The property owner has backtracked and displayed a greediness, realising that there is much to be gained and in so doing has begun to exploit the situation," he said. "It is very unfortunate that the homeowner has taken such a belligerent and selfish stance as the trust is extremely keen to uncover the whereabouts of the buried Makarov gun due to recent events surrounding Mr Mandela's health. This is highly unlikely to happen now."

'Fair and reasonable price'
He added: "It is very sad and disappointing as we very much would like to find the gun while Mr Mandela is alive."

Wolpe said there had been years of negotiations with several adjacent properties for a "fair and reasonable price". "I am extremely angry and frustrated. We've made it clear over the years that it's a negotiated purchase and we're not prepared to pay over the odds."

But Bobbie Lanham-Love, a lawyer representing 77-year-old Leenstra, insisted: "It's a reasonable price, in accordance with the price quoted by Mr Wolpe last year, not two or three times the value or anything like that. The truth is that our client could probably go to the market and realise a much higher value."

Lanham-Love accused the trust of twisting the facts to play on public sympathy: "Nelson Mandela is our greatest hero. It's so easy to hide behind the facade of an emotional argument like this." -- guardian.co.uk