ANTHONY FELDMAN came to London from Johannesburg at 18 to study at the Architectural Association. It was a brilliant period, with Rem Koolhaas among the tutors and Zaha Hadid a student.

After graduating, Feldman went to work for Rick Mather, then set up on his own. He didn’t take up minimalism — he loved pictures and beautiful things; he had collected Chinese porcelain from his teens. He liked cooking and entertaining. The champagne was always chilled and ready to open.

He lived in the top two storeys of a 1782 Henry Holland house in Mayfair. The floors and fireplace were painted in eight shades of pale grey and several shades of white. Feldman defied the present glorification of the kitchen and en suite bathrooms and hid those rooms. His large drawing-room/dining-room with the Bechstein grand and long table laid with mixed old china, napkins specially sewn in Turkey and his grandmother’s many- coloured Bohemian glasses breathed pleasure.

His first client was Jonathan Aitken in Lord North Street, and he also worked for Princess Michael of Kent in Kensington Palace, Princess Pignatelli and Sir Sydney Kentridge, QC, who defended Steve Biko in the South African courts. He had commissions in Paris, New York and Turkey and built a cube house in Hampstead. A recent job was an Art Nouveau house in Budapest. Through this he got to know and follow Hungary’s most famous actress, Eva Magyar, who was working in Britain with Kneehigh, the Cornish company.

As a tutor, later Dean, of the Interior Design faculty at AIU London (American Intercontinental University) in Marylebone, formerly the American College, he brought rigour to the subject, reinforced by teachers who had been at the AA with him.

Feldman made a success in design after dreaming of a career as a composer. In South Africa he studied composition under Adolph Hallis and Betty Pack. His instruments were piano and cello and he loved to play Gershwin.

In London he met Little Nell at a party when she was looking for a pianist to rehearse her audition for the original Rocky Horror Show. He stepped in, and neither ever forgot Ten Cents a Dance. His introduction to another friend was her dress. He asked her to dance and said “Isn’t that a Zandra Rhodes?” She said: “I am Zandra Rhodes.” He had not worn his spectacles.

Feldman’s first stage music was for Sheridan’s The Duenna at the 1984 Edinburgh Festival (performed by the music and drama students of London University). His music for Michael Fry’s adaptation of Tess of the D’Urbevilles opened in London in 1985 and was later put on by the Royal Exchange, Manchester, which toured it in 1996; it has been seen in more than 30 productions around the world.

He wrote music for, among other plays, Kleist’s Penthesilea starring Susannah York at the Latchmere, Piano Play by Esther Freud, and Entertaining Mr Sloane for the Nuffield in Southampton. For Japes by the Not The National Theatre Company, which did a four-month British tour in 2005, he wrote a haunting cello solo. He was working on a chamber opera of Cocteau’s Les Parents Terribles when he died.

Despite his talent he had no fluctuating artistic temperament or obvious charisma, although good-looking, with fine features and beautiful hands. His level-headedness and humility had emerged from an indulged early life.

He was the youngest of five children of Max Feldman, Professor of Psychiatry at Witwatersrand, who with the psychiatrist Alice Cox had established the profession in South Africa, and his pianist wife, born Rosaline Myerson.

He had a black nanny, Johanna, whom on his visits to Johannesburg he always took to the best shoe shop and then to the smartest restaurant. His two eldest sisters had moved to London before him, Joan, 17 years older, and Marion.

In 1983 he met Robert Troyan, who had come from Boston after art school. Troyan worked on many of Feldman’s projects and was also his partner in life. They were both immensely kind and generous to people in need and to charities for the homeless. Trudi Styler enlisted them for her and Sting’s campaign for Tibet.

Feldman often saved the good cause considerable sums by making the canapés himself. His feeding of people was a gesture of affection from an undemonstrative man.

His Mayfair dinners elevated the guests above superficial chatter, but he was just as comfortable cooking for locals in the Turkish fisherman’s cottage he and Troyan rented in Kekova. Feldman made mainly Turkish dishes but also served shellfish from the cove.

For the past three years he had been an honourably tight-lipped carer for his sister Joan, a psychiatrist in the NHS who had breast cancer and did not want anyone else to know.

She died in August, and in October pancreatic cancer was diagnosed in Feldman.

He and Troyan were allowed to pre-empt the official start of civic partnerships, and the Registrar Alison Cathcart united them on December 10 in their flat, among friends and four women bridesmaids — Westminster’s first couple under the new law.

Feldman’s last commission was the exterior and interiors of the Royal Asiatic Society in Pentonville, for which fire- protection and preserving the collections was as important as aesthetics. He hit on a Sir John Soane-influenced solution, bowing to the great collector-architect of the Regency, and it is going ahead.

He is survived by Robert Troyan.

Anthony Feldman, architect and composer, was born on November 27, 1953. He died on December 18, 2005, aged 52.