He served as private secretary to five successive Chairmen of the Conservative Party between 1989 and 1995, under Prime Ministers Margaret Thatcher and John Major.

[1] In 2012, he was appointed a Lord-in-waiting, and served in the Lords as a government whip and spokesman on the Cabinet Office, Business, Innovation and Skills, and Energy and Climate Change.

In May 2015, Gardiner was promoted to be Captain of the Queen's Bodyguard of the Yeomen of the Guard and Government Deputy Chief Whip in the House of Lords.

[3] He lives in London and Suffolk and is a partner of the family farm at Kimble in Buckinghamshire.

He was Chairman of the Vale of Aylesbury with Garth and South Berks Hunt from 1992 to 2006 and President of the Buckinghamshire County Show 2007.