Northamptonshire's Dowager Viscountess Dilhorne, who trained pigeons to carry World War II secret communications from the continent, has died aged 93.
During the war the then Mary Manningham-Buller trained carrier pigeons in a small Oxfordshire village.
The birds were used by secret agents and resistance fighters, flying back to her with coded messages on their legs.
The funeral of the Viscountess, who died on 25 March, will be held on Friday at Deene Park, Corby.
She was the widow of the 1st Viscount Dilhorne, formerly Reginald Manningham-Buller, who was Lord Chancellor from 1962-64.
He became the Conservative MP for Daventry, later South Northamptonshire, in 1943 and left the Commons for the Lords on becoming a peer in 1962.
For many years after the war Mary Manningham-Buller did not discuss her secret work for the government, even though she had discovered that some of the messages carried by her pigeons had been of critical importance to the military.
Lady Dilhorne was born Mary Lilian Lindsay, one of eight children of David Lindsay, Lord Balcarres.
Her mother was Constance Lilian, youngest daughter of the MP for Huntingdon Sir Henry Pelly.
The Viscountess is survived by a son and three daughters. One, Eliza Manningham-Buller, has been director-general of the Security Service since 2002.