Hubert was born in Buenos Aries, Argentina on 24 July 1904 to Alfred Duggan and his wife, Grace Elvira Hinds. His father was born and brought up in Argentina and was honorary attaché to the British Legation. His mother was a daughter of J. Monroe Hinds, former United States Minister to Brazil. After the death of his father in 1915, his mother married in 1917 as his second wife, George Nathaniel Curzon, 1st Marquess Curzon of Kedleston who died in 1925.

Hubert was educated in Goodhart's House at Eton and became Captain of the house. He came up to Christ Church in 1924 having left Eton early due to ill health and having spent several months in Argentina. He returned from there with his mother in January 1924. He came up to Christ Church in the Trinity Term 1924.

The writer, Anthony Powell, who was a contemporary, claimed that he took an intense dislike to life at Oxford falling into depression and remaining only one term. He reported that on, one occasion, he saw Lord Curzon (then Chancellor of the University) talking to Duggan who had not yet got out of bed.

In the autumn of 1927, he visited Argentina, again, with his mother and is described on the manifest as an Army Officer.

Hubert had joined the Life Guards after Oxford, but served only four years before he resigned his commission on being selected as prospective Conservative Party candidate for East Ham South in 1928.

That summer, he married Joan Molesworth Dunn, second daughter of Sir James Hamet Dunn, the Canadian financier, at St. George's Church, Hanover Square. They went to Madeira, returning to England in September. They were living at 1 Carlton House Terrace. On 1 November 1929, they were divorced and Hubert was granted custody of a son who had been born on 5 August 1929.

He was adopted as the Conservative candidate for Acton in 1930 and won the seat at the 1931 General Election. He held the seat until his death.

He was in Argentina in the summers of 1933 and 1936 and, again, in 1937 when he travelled with his long-time mistress, Phyllis de Janze [and her maid].

At the outbreak of the war, he rejoined the Life Guards as a Lieutenant, apparently in spite of medical advice. In 1940, he ceased to serve on active duty. His health declined, but he insisted that he would not be invalided out of the Army.

Phyllis de Janzé died in April 1943. That July, Duggan fell gravely ill with tuberculosis, and on 14 September he was removed from the Reserve of Officers and granted the honorary rank of Captain.

Brought up in the Roman Catholic faith of his father, from which had been estranged since his youth, he returned to it with the help of his friend, Evelyn Waugh.

He died on 25 October 1943 at 18, Chapel Street, Belgrave Square, the home which he had shared with Phyllis de Janze. The funeral was private and a Mass was held at the Church of the Immaculate Conception, Farm Street on Wednesday, 3 November at [Father Devas of Farm Street had received him back into the Church.]

He is buried in the Cemetery at Windsor, Section. H.N. 16.