Image caption An unsmoked Havana cigar owned by Churchill fetched more than £2,000

One of the largest collections of Sir Winston Churchill memorabilia, including an unsmoked cigar, has sold for nearly £600,000 at auction.

The items were sold by US publishing magnate, Steve Forbes, who amassed them over three decades.

The collection also featured a candid letter from the wartime leader, and a set of his free trade speeches.

Auctioneer Christie's says the items, being sold in three parts, provided an exceptional insight into the man.

The first sale, of about 150 lots, will be followed by a second in New York in December and a third in London next summer.

Described as "the most important and comprehensive private collection of letters and books related to Winston Churchill ever assembled", the items realised £577,063 in total.

I'm ashamed of you for writing such a letter. I return it to you to burn and forget Sir Winston Churchill , Extract of letter, June 1940

Christie's director of books and manuscripts, Thomas Venning, says one letter from June 1940 dealing with the darkest days of the war gives an unmistakable insight into his character.

He says: "One of his [Churchill's] ... former private secretaries has just written to him a letter of pure defeatism, saying, 'We've done our best. Now is the moment to make peace terms'...

"It's just a purely craven letter. Churchill's response is magnificent and simple. He just says, 'I'm ashamed of you for writing such a letter. I return it to you to burn and forget.'"

The letters sold for more than four times their estimate - going to a private UK buyer for £34,850.

In the 1940 letter, Eliot Crawshaw-Williams wrote to Churchill: "I'm all for winning this war if it can be done...

"But it does seem to me, and, I know to others, that 'if and when' an informed view of the situation shows that we've really not got a practical chance of actual ultimate victory, no questions of prestige should stand in the way of our using our nuisance value while we have one to get the best peace terms possible.

"Otherwise, after losing many lives and much money, we shall merely find ourselves in the position of France - or much worse.

"I hope this doesn't sound defeatist; I'm not that. Only realist."

An unsmoked Havana cigar offered in a box beat its estimate of £1,000-£1,500 to fetch £2,125.

The top lot was a collection of Churchill's free trade speeches, delivered in Manchester or in the House of Commons.

Estimated to fetch £20,000 to £30,000, they were bought by a private US collector for £39,650.

The former prime minister's engagement diary on 30 cards, giving details of his daily activities from September 1939 to June 1945, were expected to fetch up to £120,000, but it was withdrawn from auction before the sale took place.

Steve Forbes who gathered the collection, is chief executive of Forbes Inc and the grandson of Forbes magazine founder BC Forbes.

He said he was parting with the collection because his family did not share his passion for it.