Paul Brown, from Lewes Road, donated 'Girls in a Poppy Field' to the Berkshire fundraising event organised by the Starlight Children's Foundation, the charity which grants wishes for children with life limiting illnesses.
The full-time artist, who regularly donates his paintings to charity auctions, said: "Normally, a painting like that would sell for about £5,000 so I was amazed."
Paul watched the work go under the hammer after a hotly contested bidding war.
"There were two people who really wanted it and there was a little battle going on," he said. "It went to a man from Salisbury who said he just loved it and had to have it.
"We live at the bottom of Ditchling Beacon and my wife and two of her friends modelled for me on the Downs a couple of years ago when all the poppies were out. I took several images and used what I liked from the best ones to create the painting."
Paul's oil on canvas was painted exclusively for the Starlight Shooting Challenge which is held annually at Highclere Castle, home of the Earl and Countess of Carnarvon in Newbury, Berkshire. The auction followed a champagne reception with Girls in a Poppy Field fetching nearly one third of the £150,000 raised on the day.
Part of the money will go to help seriously ill patients at Brighton's Royal Alexandra Children's Hospital and Chestnut Tree House hospice near Arundel.
Paul, who has been painting professionally for the past 16 years, said: "I graduated with a degree in Economics from Cardiff University and worked in London for three years but became disillusioned with my job. I had always been very interested in painting and I took a leap of faith and just went for it."
His first solo exhibition was held in London in 1992 and since then he has gone from strength to strength. He has regular solo exhibitions at Gallery 47 in London and his paintings have been shown at other prestigious galleries in the city and further afield.
Paul's subject matter is wide-ranging and includes landscapes, views of the Downs, Venice and London, and figure compositions such as beach scenes featuring children playing on the sand and in the sea.
He said: "Every painting should have the 'wow' factor and, ideally, what I aim to achieve in my paintings is to arouse an emotional response from the viewer."
Paul's 'wow' factor picture at the Starlight auction will propel him further into the spotlight. His paintings are expected to command higher prices from now on, and can already be found in numerous corporate and private collections. Famous people who own his works include Sir John Major and The Duke of Richmond.
l The Attic Club of Ditchling holds its annual exhibition and sale of paintings by professional and amateur artists in the village hall from Saturday, July 5 to Sunday, July 13 from 11am to 5pm daily. There is a large, free car park behind the hall.