A painting kept in an attic for 30 years because the owner did not like it has turned out to be the work of Sir Winston Churchill.

The wartime Prime Minister painted Windlesham Moor in Surrey around 1934. The house was later the first home of the Queen and Prince Philip.

The oil painting is expected to fetch up to ?150,000 when it is sold later this month at John Dickins Auctioneers in Buckinghamshire.

The oil painting was passed on to Churchill's wartime director of Home Intelligence, Baron Stephen Taylor, who later gave it to his secretary as a gift.

She in turn passed in onto her son who, not knowing what it was, took an instant dislike to it and chose to wrap it in a bin liner and store it in his loft.

It remained there for 30 years until the painting was handed in at auction, but because it was unsigned experts couldn't put a value on it.

Auctioneer John Dickins has now carried out 10 months of detective work to establish its provenance and was delighted when he traced it back to Churchill.

The painting is of Windlesham Moor in Sunningdale, Surrey - the first marital home of the Queen and Prince Philip.

Mr Dickins, of John Dickins Auctioneers in Buckinghamshire, which is selling the painting, said: 'This is a painting which, having remained virtually unseen for much of its life and, for the past 20 to 30 years, un-loved and lying in an attic, reaches the public domain for the first time.

'There has already been a lot of interest in it.'

Describing how the painting was rediscovered, Mr Dickens said: 'When the vendor brought it in the painting was untitled and unsigned, and, at first glance, arguably unremarkable.

'But he said the painting had been presented, as a token of appreciation, to his mother in the late 1970s by her former employer, Baron Taylor.

Churchill painted many works - but didn't sign many as he did not rate his work

'He told her it was one of Churchill's works and that he had been given it by the great man himself.

'The vendor was given it years ago by his mother, who is still alive today.

'He said he had never liked it, didn't have any feeling for it and had kept it in the loft for between 20 to 30 years in a bin liner.

'He had been having a sort out in his loft and decided to get rid of it.'

The seller does not wish to be named but is aged in his 50s, comes from Oxfordshire and is a college lecturer.

Mr Dickins said: 'Now the vendor knows what it is he likes it more but still wants to sell it.

'It would be a crime to put it back in the loft and I don't think he would feel comfortable hanging a six figure painting in his home for fear of it getting damaged.

'The fact that it has been kept in the loft for up to 30 years hasn't done the painting any harm at all. There are no rips or holes and it didn't need cleaning.'

The fact Churchill didn't sign the painting was sign of his modesty about his artistic talent.

Mr Dickins said: 'Churchill was a better artist than people think, he was prolific too.

'His works come on to the market quite infrequently because people like to keep hold of them.

'He didn't sign that many paintings because he didn't rate himself as an artist.

'After the war he was persuaded to hold an exhibition at the Victoria and Albert Museum and he entered them under the false name of David Winter.

'Churchill prices have risen in the last 10 years, during which time he has been named as the greatest Briton of all time.'

Churchill enjoyed painting notable country mansions and it is believed he visited Windlesham Moor after a piece was published about its gardens in Country Life magazine in 1934, during his so-called Wilderness years.

The oil on canvas, which is 21ins x 28ins, features the estate's Brown Lakes, arched stone bridge and the main house.

All Mr Dickins had to go on to prove its origin was a scrap of paper attached to the back of the painting which had the word 'Windlesham' written on it.

He soon confirmed it was Windlesham Moor by visiting the property, which is today owned by Sheikh Mohammed bin Rashid Al Maktoum, the Prime Minister of the United Arab Emirates and leading owner in the famous Godolphin racing stables.

Mr Dickins said: 'The piece is consistent with Churchill's style and use of colour in other works by him between the two wars.

'There is a small boat in the picture and Churchill had a thing of putting boats in other work with water.

'Further corroboration is afforded by the frame and canvas.

'The frame is identical to one seen, still in its original packing, in Sir Winston's old studio at his home Chartwell in Kent.

'The canvas is clearly stamped verso with the name of his preferred supplier, Roberson and Co of London, and the address for them is the one they used before they moved premises in 1937.'

The auction takes place on September 20 and the painting, under the title Windlesham Moor, Surrey, has a guide price of between 100,000 to 150,000 pounds.