A Bridport-born diplomat who played a role in the establishment of the United Nations has died aged 101.

Sir Brian Urquhart was the second staff member hired by the international organisation following its founding in 1945 and worked as a principal adviser to five UN secretaries general in his 41-year career.

Born in Bridport in 1919, Sir Brian joined the Army following the outbreak of the Second World War, rising to Major and participating in the planning for the airborne aspect of Operation Overlord.

After the war, he served as a member of the British staff on the Executive Committee of the Preparatory Commission of the United Nations which established the framework for the organisation.

In his role at the UN, he directed 13 peacekeeping operations, recruited 10,000 troops from 23 countries and instituted peacekeeping as one of the core tenets of the organisation.

Secretary-general Antonio Gutteres said: “Sir Brian’s imprint on the United Nations was as profound as that of anyone in the organisation’s history.

"As an aide to secretary-general Dag Hammarskjold, he helped to define the UN's scope of action in addressing armed conflict and other global challenges. And as a close associate of Ralph Bunche, the renowned UN official and Nobel Peace Prize winner, Sir Brian helped to establish and then propel international peacekeeping into wide-ranging use."

Sir Brian's son Thomas confirmed he died at his home in Tyringham, Massachusetts, on Saturday but did not provide a specific cause, the New York Times reported.

Sir Brian called peacekeeping forces an army without an enemy and decided they should wear blue helmets to distinguish them from combatants. He said they should enter a war zone only with broad political support, with the goal of ending hostilities and facilitating negotiations.

He joined the Ford Foundation after he retired and wrote books and frequent commentaries for The New York Review of Books and other publications. His books include a 1987 autobiography titled A Life in Peace and War, as well as books on UN leaders and operations.

He is survived by his wife, his five children, a stepson, 14 grandchildren and 10 great-grandchildren.