Margaret Thomas studied at Sidcup School of Art and then won a scholarship to the Slade School of Fine Art. After two years she transferred to the Royal Academy, where she studied under Thomas Monnington and Ernest Jackson. During the war the school was closed and she went to work on a dairy farm and an apiary in Wiltshire. In 1945 she returned to London and began building up her career as a painter with portrait commissions and solo shows; her first show was at the Leicester gallery in 1949.
She was elected to the R.B.A. in 1947 and to the N.E.A.C. in 1951, where she has shown annually since. She exhibited her first work at the Royal Academy in 1943 and later showed at the Summer Exhibition for 46 consecutive years. She has had solo exhibitions at, amongst others, the Leicester Galleries (London), Aitken Dott & Sons (Edinburgh) and the Mall Galleries (London) and her work is held in many notable public and corporate collections including Lloyds of London, the Arts Council, Tate Britain and HRH Prince Philip.
Rivers feature prominently in her work: the Norfolk Broads (near her father's home), the Forth (overlooked by her studio in Edinburgh), the quay at Orford, Suffolk (where she bought a boathouse studio) - and the Thames, London where she grew up and lived for many years.
Influenced by Braque and Philip Wilson Steer, her work is underpinned by robust draughtsmanship and deft almost abstract design. In her paintings, as in her life, there is a down-to-earth poetry and a complete rejection of all pretentiousness.