A QUIETLY innovative scholar, John Hayes will be remembered for his directorship of the London Museum and then of the National Portrait Gallery, and as the leading expert of his day on Thomas Gainsborough.

His appreciation of that rumbustious 18th-century Englishman, “one of the most lovable persons who has ever lived”, was intense and lifelong, running through from his PhD thesis at the Courtauld Institute (1962) on the landscapes, published as The Landscape Paintings of Thomas Gainsborough (1982), to his edition of the artist’s letters in 2001. As editor in chief of the Yale/ Mellon Centre for British Art Gainsborough project, he had in draft a book about Gainsborough’s fancy, or subject, pictures when he became incapacitated last August.

John Trevor Hayes was born in London in 1929. He was educated at Ardingly College and at Keble College, Oxford, where he read history, before moving on to postgraduate study at the Courtauld.

He was a keen tennis player and an enthusiastic traveller — friends recall his delight in the 1960s in a Lancia with ruched grey curtains, and art trips to Naples, Rome and Venice in the 1980s. His longstanding passions for opera, ballet and good food he shared with his many friends. His self- depreciating humour, soft voice, warm hospitality and the occasional Op-Art — or, from 1988, Garrick Club — tie were memorable.

Hayes’s career divided into 20-year blocks, the first as assistant keeper (from 1954) and (from 1970) director at the London Museum, the second as director of the National Portrait Gallery until he retired in 1994.

The latter position gave him a public platform for several initiatives, notably commissioning portraits. In 1980 he initiated and found funding for the Portrait Award (later the BP Portrait Award). He built strong links with regional museums, inspecting Croxteth Hall, for example, with Liverpool councillors as a possible outstation, long before this became government policy.

In partnership with the National Trust, he brought paintings out from the NPG reserves for new galleries at Beningborough Hall near York and Bodelwyddan in Wales.

He pioneered the “acceptance in lieu” scheme to retain paintings in their historic setting, as with the portraits at Arundel Castle, and acquired, for example, three Van Dycks in four years, the Warwick Castle Queen Elizabeth portrait and a full-length portrait of Edward VI, as well as striking 18th-century portraits and sculpture.

At the contemporary end, portraits of businessmen, Bryan Organ’s commissioned portrait of Diana, Princess of Wales, a self-portrait by Graham Sutherland plus photographs built a strong inheritance for his successor.

After working with architects at the London Museum from 1969 to 1973 to realise the Museum of London (opened in the Barbican in 1976), Hayes instigated various ambitious but frustrated projects to extend, or find a new home for, the Portrait Gallery.

Successfully achieved when the Orange Street extension opened, this involved persuading Margaret Thatcher’s Government — notoriously uneasy about funding museum expansion — to purchase the freeholds along Orange Street in 1987.

The new galleries were an index of his quiet effectiveness in dealing with Whitehall and of his trust in his staff, since his deputy, Dr Malcolm Rogers, now director of the Museum of Fine Arts in Boston, both managed the project and attracted the essential private funds, notably a donation of £2 million pounds from the Heinz Foundation. It must have helped that the gallery hosted the 1985 London Economic Summit dinner and that the portrait of Margaret Thatcher commissioned from Rodrigo Moynihan was hanging prominently.

Nurturing talent is a gift that Hayes displayed in selecting Colin Sorensen, then the co-director of the Mellon Foundation, as head of the Modern Department at the London Museum. Because Sorensen — “the man who knows more about London history than any one else I know”, Hayes once observed — had been at the Royal College of Art, the Civil Service Commission had to be persuaded to waive its formal rubric. With innate delicacy, Hayes led by example, encouraging younger staff to stretch themselves through publishing,acquisitions and exhibitions.