Leo Beckett, who has died aged 95, was my friend and co-conspirator as each of us in our own way supported Dame Margaret Beckett MP when she was environment secretary, then foreign secretary. Leo was Margaret’s most trusted counsellor for 50 years and ran her parliamentary office; they were married for 42 of those years. I was director of communications in her departments. An outstanding Labour and trade union organiser, Leo combined efficiency with care and concern for everybody involved. He was a genius in putting everybody at their ease. The son of Arthur Beckett, a soldier, and his wife, Marjorie (nee Holland), he was born in Brompton barracks, Chatham, in 1926, the year of the general strike, as he never failed to point out. He was named Lionel, but always known as Leo. Towards the end of the second world war, aged 18, he joined the RAF. These were formative years. His learning from fellow servicemen from mining and other working-class communities transformed his own political understanding. His family had settled in Leadenham, Lincolnshire, and after his RAF service Leo was taken on as an apprentice, then offered a job, with the Lincoln engineering company Ruston Bucyrus (later taken over by GEC). He soon became an influential figure in Labour politics in the city. After the deselection of Dick Taverne (now Lord Taverne) as Lincoln’s Labour parliamentary candidate in 1972, Leo helped Margaret Jackson, the party’s new candidate, to win the seat back for Labour in October 1974, and they married in 1979. Leo joined Margaret to win Derby South in 1983 and hold it ever since. Beneath an effortless affability and humorous, at times cheeky, charm was a smart operator, adept in navigating turbulent waters at Westminster, in Margaret’s constituency in Derby South, and at Labour party conferences. Leo held deep values expressed through his love of, and loyalty to, the Labour party and Margaret herself. The Becketts shared a steely sense of common purpose and were one of parliament’s most successful partnerships. Except for the past two years, when his ill health made mobility difficult, Leo was always by Margaret’s side, working tirelessly well into his 90s and adapting to at least 10 changes in party leadership, including Margaret’s own brief spell as leader after John Smith’s death. This included supporting Margaret as a member of every Labour government since Harold Wilson was prime minister. Leo and Margaret only properly switched off when they enjoyed their caravan holidays. Modest, with a genial personality, Leo made everybody feel that they were special and made friends across the political spectrum. He was predeceased by his first wife, Beryl Firth, and their two sons, David and Roger. Leo is survived by Margaret, and by his three grandchildren, Alison, Vicky and Jon.