Hardcastle was born in Newcastle upon Tyne, and educated at the Newcastle Preparatory School and Durham School. His early intention to follow his father into the medical profession was thwarted when he contracted osteomyelitis as a fifteen-year-old, and in 1938 he joined the Shields Gazette as a reporter.
Durham School.
Unfit for active service, Hardcastle remained a journalist throughout the Second World War, moving in turn to the Sheffield Telegraph, the London bureau of Kemsley Newspapers and Reuters. In 1944 he became Reuters’ correspondent at Supreme Allied Headquarters, followed by postings to New York and Washington. In 1959 Hardcastle was appointed editor of the Sunday Dispatch, and after two months in that job was moved to become editor of the Daily Mail until 1963, covering the period when it absorbed the News Chronicle.
He moved into broadcasting.
On 4 October 1965, he became the launch presenter of The World at One on the British Broadcasting Corporation Home Service and then British Broadcasting Corporation Radio 4. He retained this role until his death in 1975, and from 1970 hosted the Prime Minister programme, as well.
