It was the start of a passion for the Leeds doctor, who now has hundreds of paintings, sculptures, prints, photographs, manuscripts and books.
Dr Sherwin is the proud owner of what is widely regarded as one of the most significant collections of British Surrealism.
And this summer it will form the leading exhibition at the new £14.2m Middlesbrough Institute of Modern Art (Mima).
While some works have been shown in galleries in the UK and abroad it will be the first time so many pieces from the collection have been in a major exhibition.
Dr Sherwin, an honorary alderman and former chairman of Leeds Leisure Services, started collecting in 1986. He was inspired after visiting an exhibition at Leeds Art Gallery commemorating the 50th anniversary of the first international surrealist exhibition at the New Burlington gallery in London, which featured works by artists including Picasso and Max Ernst.
With his interest sparked, Dr Sherwin bought his first work – Merlyn Evans The Chess Players – which shows Molotov and Ribbentrop playing chess for Europe to illustrate the 1939 Russo-German non-aggression pact. Dr Sherwin said: "I was very naive in those days as a collector. The price was £1,250 and my fingertips perspired as they had when I thought I couldn't do my physics A level exam.
"(The London dealer] reduced the price considerably and after buying the print I asked him if he thought the work he was selling was any good."
The Mima exhibition came about when Dr Sherwin visited the gallery. He said: "I was talking to the director, who I knew, and he came to Leeds to see my collection and was keen to mount an exhibition."
Artists to be featured in the exhibition will include Eileen Agar, Roland Penrose, Henry Moore, Conroy Maddox and Desmond Morris, the anthropologist author of The Naked Ape. Some have Leeds connections – Anthony Earnshaw worked and taught at Leeds College of Art, Patrick Hughes also taught at the college and Glen Baxter was a student there.
Dr Sherwin, who has previously loaned pieces to Leeds Art Gallery, said: "If Leeds wanted to mount a similar exhibition I would be happy. I feel part of me belongs to Leeds City Art Gallery."
British Surrealism and Other Realities: The Sherwin Collection opens at Mima on May 23 and runs until August 17.