Brook was educated at Wolverhampton Grammar School and Wadham College, Oxford.

"[4] Brook joined the Home Civil Service in 1925 and attained the grade of Principal in 1933 and of Assistant Secretary in 1938.

He was also joint permanent secretary to HM Treasury and head of the Home Civil Service from 1956 to 1962.

[7] On 24 January 1963 he was raised to the peerage as Baron Normanbrook, of Chelsea in the County of London.

He was one of the twelve pall bearers at Sir Winston Churchill's funeral in 1965.