A lost painting by one of the most influential portrait artists has gone on display in Regent’s Park.

The Royal College of Physicians, St Andrews Place, has unveiled Sir Anthony Van Dyck’s portrait of Dr Baldwin Hamey, a former registrar at the college and one of their most generous benefactors.

The whereabouts of the 17th-century portrait had been unknown for centuries before its most recent owner, an American collector, contacted the college to research its origins.

The college was then able to acquire the painting, with the support of the V&A Purchase Grant Fund and the Museum Association’s Beecroft Bequest.

Dr Hamey was a registrar at the college from 1646, becoming treasurer in 1664. He donated generously to the college throughout his life, helping to fund its rebuilding after the Great Fire of London.

Dr Bendor Grosvenor of Philip Mould, a gallery specialising in old masters and British pictures, will give a lecture on the painting on Monday at 6pm.

The Royal College of Physicians holds more than 5,000 pictures of individuals associated with the history of medicine.