The National Portrait Gallery (NPG) in London has acquired a controversial 17th century painting which was lost for nearly a century.

The portrait, by court artist Sir Peter Lely, is of King Charles II’s leading mistress – Barbara Villiers, Duchess of Cleveland – with his son and was painted circa 1664.

It was bought for £147,000 with the proceeds of a public appeal and additional financial support from the National Heritage Memorial Fund, the National Art Collections Fund, the Camelot group, members of the Chelsea Arts Club and a selection of individual donors.

The painting challenged portrait conventions of the time and depicts the King’s mistress and son as figures of religious veneration – Villiers was a household name in her day.

Speaking about the acquisition, the director of the gallery, Sandy Nairne, said: “This is an intriguing, wonderful portrait. I am grateful to all those who made the acquisition possible.”

The NPG – which boasts the most comprehensive collection of its kind in the world – was founded in 1856 to collect likenesses of famous British men and women and is located at St Martins Place, near Charing Cross. Details: www.npg.org.uk