This portrait of Churchill is incredibly rare, and could fetch an eyewatering sum at auction

A very rare, and signed, portrait of Britain's most famous Prime Minister is about to go up for auction - and could attract an eyewatering sum.

Artist Paul Trevillion drew the pen-and-ink portrait of wartime leader Winston Churchill in 1955. It was drawn after he famously ordered another painting to be destroyed.

Now, the artwork is believed to be capable of fetching around £1m when it goes up for auction at Hansons Auctioneers.

Trevillion was inspired to paint a smiling Churchill after the former PM bitterly complained about a portrait by artist Graham Sutherland a year earlier.

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Churchill famously hated Sutherland's painting which had been commissioned for his 80th birthday showing him slumped in a chair and staring blankly ahead. On seeing the painting, he told his private secretary, Anthony Montague Browne, "I look like a down-and-out drunk who has been picked out of the gutter in the Strand."

It was reportedly thrown onto a bonfire a month after Churchill's death in January 1965 on the orders of his wife Clemmie. In direct contrast, Churchill was so impressed by Mr Trevillion's upbeat portrait, he summoned the artist, aged 21, to sign the work.

The painting is now set to sell for at least £100,000 but could fetch up to £1 million when it goes under the hammer. Mr Trevillion, now aged 90, insured the painting for £1 million when it was displayed at Manchester's National Football Museum in 2017.

The artist, from Tottenham, North London, plans to donate some of the proceeds of the auction to charities. He recalled challenging himself to create a painting of Churchill after Sutherland's portrait fiasco.

Mr Trevillion said: "Unfortunately, Churchill's birthday was ruined by the Sutherland portrait, so I decided to do another portrait for his next birthday. My drawing was based on images I'd seen of Churchill when I was a child in the Blitz.

"I was five years old when war broke out in 1939. Churchill was always smiling, with his famous V for victory sign. Those images of him helped me cope with the night-time raids."

The portrait was presented to Churchill, who was then retired, by his friend, Bernard Sunley, with the help of designer Lazslo Hoenig.

"Imagine my surprise when, a week later, sitting working in Hoenig's studio, I was told that Sir Winston Churchill was on the phone," said Mr Trevillion. "'Hello,' Churchill said, in his deep voice. 'Is that Trevillion?' I said, 'Yes.'

"He said, 'Winston here. I will be at the Bernard Sunley Buildings, Berkeley Square, on Wednesday, 10.30. Oblige.'

"When I walked into the room, Churchill was seated. He put out his hand. I went to shake it, and he held it. He said he was expecting someone much older. He asked if I'd been evacuated in the war, which I hadn't. 'You're a boy from the Blitz.'"

Churchill signed the picture, telling the young artist: "There have been a lot of portraits painted of me, but this one I really like. It's the only one I've ever signed."

Mr Trevillion stored his treasured artwork in a bank safe deposit box for 69 years but now feels it is time to sell it. Neil Barker, manager of Hansons' Churchill150 Auction, said: "It is arguably the most important Winston Churchill portrait in existence."

"Perhaps it resolved the despair he felt when he saw the Sutherland portrait of himself slumped in a chair. It was not how he wanted to be remembered in his old age."

Mr Trevillion's Churchill portrait will be sold on November 20 at The RAF Club, Piccadilly, London.