A quietly-persuasive campaigner able to influence the highest circles of government, the Dowager Countess of Albemarle, has died aged 103.

After just one year as chairman of the Norfolk Federation of Women's Institutes in 1945, she was elected the following year as national chairman.

In post-war Britain, and with her non-party background, she was rapidly recruited by Whitehall and Downing Street to head a number of important non-government bodies. In October 1948, she became the first woman chairman of the Development Commission, serving for almost a quarter of a century, and helping to improve the agricultural and rural economy.

A month later, she and husband, now the 9th Earl of Albermarle, announced the sale of the family's seat and grounds at Quidenham Hall – now the home of the Carmelite convent and also East Anglian Children's Hospices – and moved to near Ipswich.

However, she maintained her close links with Norfolk and was a member of the council of the newly-created University of East Anglia between 1964 and 1972.

She had been made a Dame of the British Empire in 1956 in recognition of her contributions to so many organisations and bodies including the Arts Council from 1951.

In 1960, the government accepted within hours of publication almost all the main recommendations of the two-year departmental committee into youth service, which was then known as the Albemarle Report. It was to lead to a near-doubling of investment into youth funding within the next five years.

Born on August 6, 1909, Diana Cicely Grove was an only child and her father was killed during the first world war. Educated at Sherborne School for Girls, Dorset, the 13-year-old had fought a battle to be allowed to board.

In February 1931, she was 21 years old when she married the widower Viscount Bury, who was almost 30 years her senior, and acquired an instant family of five step-children. They moved to Quidenham where during the depression, her husband tried to organise employment relief for women on his estate, partly by working with the WI.

As a result, in 1933, Lady Bury became president of the newly-formed Snetterton Women's Institute, which she later admitted was the start of what became decades of public service. In 1940, she was elected to the Norfolk executive committee, became vice chairman in 1944 and WI chairman the next year.

She was a member of Wayland rural district council between 1933 and 1946.

She had become a Roman Catholic in the late 1930s, prompted partly by her experiences in pre-Anschluss Austria. On holiday in the Tyrol, a few weeks before Adolf Hitler's arrival in March 1938, she had a hunch which made her send home for more pound notes. When Hitler marched, she bought tickets home for the nanny and children but went to Vienna to help friends and see what could be done. There she was impressed by the Roman Catholics' strength to endure. It was about the same time, she also left the Conservative Party, recognising that no party had the monopoly of wisdom.

In 1939, she became Norfolk county organiser of the Women's Voluntary Service for Civil Defence, which had been set up by government a year before, and stood down in 1944. Then the WI demanded more of her attention.

As WI chairman for the first time in May 1947, in front of 5,000 members at the Albert Hall, London, she reported an increase of more than 350 institutes and a rise in membership of more than 45,000. She spoke strongly about the role of women in work and noted, for example, how few women held senior positions in the ministry of agriculture. Lady Albemarle – her husband had succeeded in 1942 – was county vice-president of the St John Ambulance Brigade Nursing Cadets. As she remarked on a visit to Great Yarmouth in September 1944, the first of what became 50 divisions had been formed in the town. Always determined to get things done, in July 1949, she led a deputation of the minister of health on behalf of the WI to seek improvement in rural water supplies and sewerage. She gave the example of the Waveney Valley village of Wortwell, where water was unfit to drink and wells had run dry.

She had been named 'British Mother of 1950' by the American Mothers' Committee – at that time, she had a daughter, Anne-Louise, four step-children and 10 step-grandchildren.

When she stepped down from the WI, she sat on several Royal Commissions including one on civil service pay and was on the University Grants Committee. In a feature in the Observer on St Valentine's Day, 1960, she was described 'as a committee-woman of brilliance,' with genuine charm and an ability to compromise. She knew exactly how far to push in order to achieve her goals.

After moving to Beacon Hill, outside Ipswich, where she enjoyed gardening in the grounds of her Regency house – and keeping a few black-faced ewes – which she also opened for St John Ambulance. Her other love, apart from collecting rare and unusual plants, were dachshunds.

Having missed an opportunity to go to university, partly her choice, she was delighted to receive an honorary degree from Reading and a year later an honorary degree of Doctor of Civil Law from the then prime minister and university chancellor, Harold Macmillan, in June 1960.She held a succession of posts involved with youth service, was chairman of the National Youth Employment Council and served on the Youth Development Council for most of the 1960s. And in September 1965, she visited Norwich to open officially the £12,000 Thorpe Youth Centre.

Her husband died in July 1979, aged 97. She died on May 6 having moved from Suffolk to Haddington, near Edinburgh, to be closer to her daughter.

A funeral Mass will take place at the Church of St Thomas of Canterbury, Woodbridge, on Thursday, May 16 at 11.30am where her only daughter, Lady Anne-Louise Keppel, was married in 1954 to Capt Sir Hew Hamilton-Dalrymple.

Michael Pollitt