Jean Tait, our mother, who has died aged 96, was a founder member of the Trotskyist Socialist Review Group (SRG) which developed into the International Socialists and subsequently into the Socialist Workers party. Much later, she was the first elected chair of the University of the Third Age (U3A) in London .

Jean was the youngest of three girls. Her father, Andrew Smith, a clerk at the Western Canadian Lumber Company, died suddenly in Vancouver before Jean’s birth. Her mother, Marion (nee Johnson), a primary school teacher, returned to her home town of South Shields, where Jean was born. She studied history at Westfield College, University of London, and graduated in 1940 with a first-class degree. In 1942 she volunteered to join the army and eventually served in the Education Corps.

In 1945, Jean became a member of the Revolutionary Communist party (RCP), followers of the ideas of Leon Trotsky. Through the RCP, she met Danny Tait, recently arrived from Palestine. In 1950, 21 people crammed into their basement flat in Camden, north London, for the founding conference of the SRG. From such a small beginning grew a movement that over the years has attracted tens of thousands of members. Jean remained politically active in the group until the mid-1960s. To the end of her life, she remained very firmly on the socialist left.

Jean worked in the civil service for 30 years. Following her retirement in 1975, she did voluntary work: teaching English as a second language to otherwise isolated women and then as a Citizens Advice Bureau adviser.

With a passion for continuing education, Jean was part of a small group in the early 80s that established the London branch of the U3A, the programme which enables the over 50s to organise a wide range of self taught educational courses and social events. For many years Jean was on the committee, worked in the office and later ran a popular and therefore repeated course on completing cryptic crosswords.

When Dan retired, in 1990, they were able to enjoy more leisure activities. He died in 2006 and Jean faced up to her loss with typical lack of self pity. Although increasingly frail, she remained determined to be independent for as long as possible. Four years ago she moved into a care home.

She is survived by us, her two children, and by her grandchildren, Hannah and Jonathan.