The government could have bought Winston Churchill's personal papers for a fraction of their price, records made public for the first time reveal.
The collection includes Churchill's 'Finest Hour' speech
Churchill's heirs spent two decades trying to sell the vast collection, which was eventually bought using £12m of National Lottery money in 1995.
But in 1971, the papers could have been bought for a mere £100,000, it emerged.
The collection of about 2,000 boxes of documents includes Churchill's own copy of the "Finest Hour" speech.
Files released to the National Archive in Kew on Wednesday shed some light on the lengthy negotiations that led to the government eventually paying a price seen by many as excessive for documents part of which were, by nature, "state documents".
The first attempt to sell the papers was made in 1971.
GOING, GOING, GONE...
1965: Churchill dies and papers put in trust on behalf of grandson Winston Churchill
1971: Offer of £100,000 by trustees refused by government
1989: Government asked for £15m to transfer ownership of the collection to British Library, but negotiations stall
1995: Bought for £12m using National Lottery cash
The statesman's grandson and heir, also called Winston, did not want to donate the collection of documents to the archive centre at the Churchill College in Cambridge without making any profit from it.
Sir Winston's former private secretary Sir Jock Colville, one of the papers' trustees, wrote a letter to the then Cabinet Secretary Sir Burke Trend explaining the situation, trying to broker a deal.
Sir Jock said the papers were Churchill Jr's "most valuable asset", and said Sotheby's had estimated they would fetch "something in the neighbourhood of £2m".
Winston's father had been "a very large spender" and it would have been "a bit rough" if he just had to surrender the papers without getting anything in return, he added.
"Would you like to think over the possibility of HMG making the offer of say, £100,000 or perhaps £120,000 to acquire the entire ownership of the Churchill papers, which are in fact a very important historical asset to this country?" he wrote.
But Trend replied that many of the papers were official documents which already belonged to the state anyway, and that there were no public funds to meet Mr Churchill's request.
Another 18 years passed before it emerged that Sotheby's had once again been asked to value the papers.
This time, a tip-off from the Churchill College in Cambridge revealed the trustees were considering transferring ownership of the collection to the British Library to allegedly prevent it being broken up and sold abroad.
They asked the government to pay a "fair sum" of £15m.
Former Tory chairman Norman Tebbit wrote to then Prime Minister John Major in 1991 on behalf of the Churchill family.
He explained the trustees had to sell the collection "in the interest of the beneficiary", and offered to act as intermediary. "I am told the sum would not be huge," he wrote.
The file does not contain any record of the following negotiations.
The documents, still kept at the Churchill Archives Centre in Cambridge, include his personal correspondence with kings, presidents and leaders, and can be consulted by appointment.