She began her writing career with a satirical poem in German, and wrote stories for the BBC Radio programme Children's Hour.
In 1960, she became a member of the Committee of 100 to take non-violent direct action against nuclear power, and successfully campaigned with her husband David Markham for the release of the Soviet dissident Vladimir Bukovsky.
[2] By age 18, Dehn authored a satirical poem, Goebelchen (English: A Half Aryan Ballad),[2][5] describing Nazism as seen by a Dachshund.
[3] This was the catalyst of her arrest by the Gestapo and subsequent deportation from Germany under armed guard one year later,[1][5] after the poem was intercepted at the German border en route to Punch in London.
[2] Back in England, Dehn wrote stories for the BBC Radio programme Children's Hour,[1] where she used her high-pitched voice to portray boy characters.
[3] In 1935, she signed a deal to publish her works with Basil Blackwell in a series based first featured in the Joy Street annuals,[6] and wrote the children's stories,[2] Tales of Sir Benjamin Bulbous, Bart and The Basement Bogle.
[4][7] After the Second World War, she moved into the 5.5 acres (2.2 ha) Lear Cottage,[2] near Coleman's Hatch in the Ashdown Forest, East Sussex.
[1] She was involved in non-violent direct action against nuclear power,[2][3] and was arrested and deported from Moscow by the KGB in 1974,[1] for protesting against the abuse of psychiatry in the Soviet Union.