Background
O'Neill was born on 6 February 1907 to The Hon Arthur O'Neill and his wife Lady Annabel Hungerford Crewe-Milnes. His mother was the eldest daughter of Robert Crewe-Milnes, 1st Marquess of Crewe.
O'Neill was born on 6 February 1907 to The Hon Arthur O'Neill and his wife Lady Annabel Hungerford Crewe-Milnes. His mother was the eldest daughter of Robert Crewe-Milnes, 1st Marquess of Crewe.
He was educated at Eton College, an all-boys public school in Eton, Berkshire, England.
He served during World War II and was killed in action. He did not attend university. After his death she remarried, firstly to the 2nd Lord Rothermere, a press tycoon and former Tory MP, and later to Ian Fleming, the creator of James Bond, as well as having affairs with the Labour politicians Hugh Gaitskell and Roy Jenkins.
In 1929, O'Neill joined the Gillett Brothers Discount Company as a director. Military service
On 30 August 1929, he was promoted to lieutenant in the 8th King's Royal Irish Hussars. With the outbreak of World War II, he was granted an emergency commission on 20 September 1939 as a second lieutenant in the North Irish Horse.
In October 1939, he was granted the acting rank of captain. In December 1939, he was appointed the officer commanding of A Squadron. As the 2nd Baron O'Neill's eldest surviving son, Shane's father was heir to the title of Baron O'Neill.
At his birth, Shane became second in line to the title of Baron O'Neill. As a hereditary peer with a of the United Kingdom, he was able to sit in the House of Lords. Though he had inherited the title in 1928, he first took his seat in the Lords on 3 April 1930.
In 1937 he attended the Coronation of George VI at Westminster Abbey and paid homage to him with the other Lords Temporal.