The Duke of Grafton, who has died four days after his 92nd birthday, was one of the nation's major conservationists and preservationists.

In the House of Lords, he spoke on preservation and the arts and was involved with many of the country's best-known museums and galleries.

He was made a knight of the garter in the throne room of Windsor Castle alongside the former prime minister, Sir Harold Wilson – later Baron Wilson of Rievaulx – in June 1976.

Hugh Denis Charles FitzRoy was educated at Eton and Magdalene College, Cambridge, and succeeded his father to the title in 1970 as 11th duke.

As a captain in the Grenadier Guards, he was an aide-de-camp to the last viceroy of India, Earl Mountbatten of Burma.

He ran the family's 11,000-acre estate at Euston, on the Suffolk border with Norfolk, which included extensive woodland, until handing over the active management to his late son.

He was vice-chairman of the National Portrait Gallery for 25 years until 1992 and was a member of the Royal Fine Art Commission for three decades. He served on the Historic Buildings Council and later its advisory committee for almost half a century until 2001.

The duke studied art at Regent Street Polytechnic: his father had been an accomplished watercolourist. He held his first exhibition in London in 1962. A quarter of a century later, he took up his brush again in earnest and exhibited in June 1989 at the Malcolm Innes Gallery, in London. It was a success, and more than three-quarters of the 62 paintings, mainly landscapes and floral subjects, sold for between �275 and �900.

At national level, he also chaired the Society for the Preservation of Ancient Buildings in 1967 and was president from 1989. He chaired the Architectural Heritage Fund for almost two decades and was on the executive committee of the UK Council for the European Archi-tectural Heritage Year in 1975.

Equally passionate about his native county, he was made a deputy- lieutenant of Suffolk in 1973. In January that year, when he became the first president of the East Anglia Tourist Board, he was described as 'one of the greatest preservationists in East Anglia'.

He was also chairman of the National Trust's East Anglia regional committee.

In 1957, the duke became president of Suffolk Preservation Society, a title he still held at his death. He campaigned to highlight the failure to safeguard the nation's heritage in the 1990s, determined to save Heven-ingham Hall, in Suffolk – once described as the country's finest Palladian mansion.

The duke took his farming seriously and was twice president of Suffolk Agricultural Association: in 1965 and again in 1977. There came a poignant decision in May 1987, when he dispersed the Euston herd of Poll Herefords, established more than 30 years earlier. The 44-cow herd had been bred from a second shipment of New Zealand-bred Herefords imported into Britain in the mid-1950s. He had become patron of the Hereford Herd Book Society in December 1977.

He married Fortune, now the dowager duchess, in 1946 and they had two sons and three daughters. Their eldest son, the Earl of Euston, died in October 2009 aged 61.

The duke's grandson, Harry, Viscount Ipswich, succeeds to the dukedom, created by King Charles II in 1675 for Henry Charles FitzRoy.

A private funeral will be held for family and estate staff at St Genevieve's Church, Euston, on Friday, at 3pm.

A memorial service will be held later at St Edmundsbury Cathedral, Bury St Edmunds.

Michael Pollitt