John Cartwright, who has died aged 90, was the last president of the short-lived Social Democratic party, after much of it had merged with the Liberals to form the Liberal Democrats. He was one of those rare politicians whose unassuming characteristics belied a sharply instinctive understanding of politics far exceeding that of many of the better-known figures who strode the national stage during his four decades in public life.
He was MP for Woolwich in south-east London for 18 years from October 1974, first (for Woolwich East) on behalf of the Labour party and subsequently as a member of the SDP, for which he won the seat twice, in 1983 and 1987 – securing the best result in the country for the new party in 1983, thus demonstrating his personal popularity and the respect he had deservedly won from his constituents.
Cartwright left the Labour party in February 1981, the 12th Labour defector among 29 MPs (of whom there was one Conservative) to join the fledgling SDP. He was persuaded to do so by one of the “Gang of Four” founding members, Shirley Williams, whose parliamentary private secretary (PPS) he had been in 1976-77, when she was education secretary.
He had already attempted to secure radical reforms within the Labour organisation as it drifted towards what he called “the brink of irrelevance”, having helped found the Manifesto Group of MPs to fight the growing authority of the party’s leftwing shortly after his election in 1974. He later chaired the organisation from 1977 until he resigned from the party. He said at the time that he was leaving Labour not because he had changed his views, but because he was incapable of changing his views according to the party’s then current orthodoxy. Although he would later applaud the modernisation of the Labour party, he declared socialism to be a “dead duck” in a Guardian article in 1991.
One uncomfortable irony of his apostasy was that Cartwright had inherited the then Woolwich East seat when the incumbent, the former Labour minister Christopher Mayhew, for whom he had been agent at the two previous general elections, had defected to the Liberal party in 1974. Cartwright had denounced him at the time, only to face painful accusations of treachery himself from local party members when he took a similar path seven years later.
After another seven years, in 1988, he would be attacked once again on the same grounds – this time by Liberal activists – for resisting the merger between them and the SDP.
His profound knowledge of the byways of politics coupled with his intuitive skills had swiftly made him an invaluable member of the SDP and he was elected to its national committee in 1982. He became the party whip after the 1983 election that the party had fought in alliance with the Liberals, but had already expressed his antipathy to merging the parties. He had rejected joint selection of parliamentary candidates as a “step to suicide”, and when discussions about a formal alliance were advanced by the Liberal leader David Steel after the 1987 election, by which time Cartwright had become vice-president of the SDP, he opposed being “railroaded into a shotgun wedding”.
He had become close to the SDP leader, David Owen, who valued his shrewdness and strategic ability, and when the merger into what became the Liberal Democrats went ahead in 1988, only Cartwright (who became president until the party folded) and one other MP, Rosie Barnes, remained loyal to Owen’s SDP rump. Even after the party was wound up, having polled behind the Monster Raving Loony candidate in the 1990 Bootle byelection, Cartwright came within striking distance of holding Woolwich in 1992 when he fought as an Independent Social Democrat, losing only by just over 2,000 votes.
Born in Lincoln, the son of Ivy (nee Billie) and Aubrey Cartwright, who worked variously as a salesman, a book-keeper, a fireman and a biscuit company manager, John went to the city’s Monks Road primary school before the family returned to their native Surrey.
He first campaigned for Labour as an 11-year-old in the 1945 postwar election, and became a member aged 17 while still a pupil at Woking county grammar school.
On leaving, John joined the civil service for three years from 1952, while undertaking correspondence courses through the National Council of Labour Colleges. He met Iris Tant, who worked for the electricity board in Reigate, after he had joined the Labour party staff as an organiser, and they married in 1959. In 1967 he was elected to Greenwich borough council, of which he became leader (1971-74), and he stood unsuccessfully against Edward Heath in Bexley in the 1970 election that took the Conservative leader into Downing Street. In February 1974 he stood in Bexleyheath, again unsuccessfully, as a Labour and Co-Operative candidate.
He had become the political secretary of the Royal Arsenal Co-operative Society in Woolwich in 1967, and after five years he became the director. RACS was highly political, one of the most successful co-ops in the country with a turnover of £74m when Cartwright left on being elected to the Commons. This job also brought him into membership of Labour’s powerful national executive committee, which he joined as the representative of the Labour societies in 1971 and remained a member of until 1978 – except for one year, 1975-76.
Cartwright was an assiduous and effective MP with a wide range of interests, of which his main focus was local government, environment and defence. He was admired and liked even by those with whom he disagreed, and in 1970 became a justice of the peace in inner London in 1970.
For the SDP he was environment spokesman (1981-87), a valued member of the select committee on defence (1979-82; 1986-92), and from 1983 until its breakup was the party’s frontbench spokesman on defence and foreign affairs. This was not an easy post because of differences between the SDP and the Liberals on modernising the British nuclear deterrent, but the controversy blew over after the merger split. In 1985 he co-authored a book on the search for a nuclear consensus in Europe.
The commitment to public service he showed at Westminster did not diminish when he left the Commons. Having been a member of the Layfield committee on rates reform in 1974 and of the Calcutt committee on privacy (1989-90), he was appointed to the Police Complaints Authority in 1992 and served as deputy chair until 1999. He subsequently served as a non-executive director of Lambeth, Southwark and Lewisham health authority (1995-2000) and Maidstone and Tunbridge Wells NHS Trust (2000-03).
Iris died in 2014. He is survived by their children, Neal and Lynn.
• John Cameron Cartwright, politician, born 29 November 1933; died 18 November 2024
