Barber was appointed Chancellor of the Exchequer by Edward Heath in 1970 after the early death of Iain Macleod, serving in that capacity until 1974. He became Chairman of Standard Chartered Bank after retiring from front-line politics in 1974, and served from 1974 to 1987.
Barber was educated at King Edward VI's Grammar School in Retford,Nottinghamshire. He became an articled clerk, but joined the King's Own Yorkshire Light Infantry shortly before the Second World War started. He was commissioned into the Territorial Army Royal Artillery in 1939 and served in France with a unit from Doncaster as part of the British Expeditionary Force. He was evacuated from Dunkirk in 1940, but later he became a pilot in the Photographic Reconnaissance Unit of the RAF. He ran out of fuel on a reconnaissance mission on 25 January 1943 and ditched near Mont St Jean, but was captured by the Germans. He was mentioned in dispatches for helping escapes from the prison camp at Stalag Luft 3: he himself once escaped as far as Denmark. While still a prisoner, he took a law degree with first-class honours through the International Red Cross. On his return to England, he was awarded a state grant to Oxford University, where he took a degree in Philosophy, Politics, and Economics in two years at Oriel College, and a scholarship to the Inner Temple. He then practised as a barrister from 1948, and specialised in taxation.
His absence from Parliament was short-lived, as in 1965 he won the by-election in Altrincham and Sale caused by the elevation to the peerage of Frederick Erroll. In opposition, he led Ted Heath's campaign to become Conservative party leader in 1965, and became party chairman in 1970. The Conservatives won the general election in 1970, and Barber held his seat until the general election of October 1974, when he himself entered the House of Lords.
Barber also reduced direct taxes. High levels of economic growth followed, but the traditional capacity constraints of the British economy - especially currency and balance of trade concerns - quickly choked the economic boom. The banking system fell towards crisis as the bubble burst.
During his term the economy suffered due to stagflation and industrial unrest. In 1972 he delivered a budget which was designed to return the Conservative Party to power in an election expected in 1974 or 1975. This budget led to a period known as "The Barber Boom". The measures in the budget led to high inflation and wage demands from Public Sector workers. He was forced to introduce anti-inflation measures in September 1972, along with a Prices Commission and a Pay Board. The inflation of capital asset values was also followed by the 1973 oil crisis which followed the Yom Kippur War, adding to inflationary pressures in the economy and feeding industrial militancy (already at a high as a result of the struggle over the Industrial Relations Act 1971).
After a strike by the miners, and a three-day week, Heath called for a general election on 28 February 1974, asking "Who governs Britain?". The election returned a minority Labour Government and Harold Wilson as Prime Minister.
He suffered from Parkinson's Disease in later years, and died in Suffolk in 2005. He was married twice, with two daughters from his first marriage.