His father, an army officer, died from a long-term injury when Benenson was nine, and he was privately tutored by W. H. Auden before attending Eton College.
At the age of sixteen, he helped to establish a relief fund with other schoolboys for children orphaned by the Spanish Civil War.
[5] After demobilisation in 1946, Benenson began practising as a barrister before joining the Labour Party and standing unsuccessfully for election at Streatham in 1950 and for Hitchin in 1951, 1955, and 1959.
Benenson had said he was shocked and angered by a newspaper report of two Portuguese people sentenced to prison for subversion during the regime of António de Oliveira Salazar.
[6] At the time, Portugal was ruled by the authoritarian Estado Novo regime, and anti-regime conspiracies were vigorously repressed by the Portuguese state police and deemed anti-Portuguese.
To co-ordinate such letter-writing campaigns, Amnesty International was founded in London in July 1961 at a meeting of Benenson and six other men, who included a Conservative, a Liberal and a Labour MP.
[10][11] Benenson died of pneumonia on 25 February 2005 at the John Radcliffe Hospital, Oxford, aged 83, having been a resident of the nearby village of Nuneham Courtenay where he was buried.