[citation needed] Together with his brother Norman, Leslie's early education began at home where a German governess, Clara Woelke, was their first teacher.

Not overly impressed by Eton, as a lower boy he and his roommates occupied "an old battered warren betwixt the chapel cemetery and Wise's horse yard ... [T]he food was wretched and tasteless ... As for thrashings which tyrannised rather than disciplined our house, they were excessive.

[citation needed] In the January 1910 general election Leslie stood as the Irish Parliamentary Party candidate for the Londonderry City division, losing by just 57 votes.

In the 1918 election the Irish Parliamentary Party lost massively to Sinn Féin, putting an end to Shane Leslie's political career, but as the first cousin of Winston Churchill he remained a primary witness to much that was said and done outside the official record during the negotiation of the Anglo-Irish Treaty of 1921.

He also wrote Mark Sykes: His Life and Letters (1923), a biography of the English traveller, Conservative Party politician and diplomatic advisor.

In his unpublished memoirs, he wrote "a gentleman's standing in his world was signalled by his list of clubs and it was worth paying hundreds of pounds in subs".

They continued to maintain their lifestyle, involving attendance at the London season and the entertainment of distinguished visitors, including Anthony Eden at Glaslough.

[8] He died at 15b Palmeira Court, Hove, Sussex on 14 April 1971, aged 85 and a requiem mass was held for him in Westminster Cathedral on 12 October 1971.