Hopkirk is raised as a Catholic, and educated at Clongowes Wood College in County Kildare from 1945 to 1949 before attending Trinity College, Dublin until 1953. His academic career, however, is held back by his dyslexia. He first learns the basics of car control at the age of nine, when a local clergyman leaves him his invalid carriage in his will. He later graduates to a motorcycle with a sidecar, which is added at the insistence of his father who feels it would be safer, and upon attending Trinity to study engineering, acquires an Austin 7 “Chummy” Tourer which he uses to make his rally debut. Now bitten by the car bug, he drops out of university to start working for Dublin‘s Volkswagen assembler’s retail operation in Ballsbridge, where he purchases a string of used Volkswagen Beetles to enter in competitions.
Hopkirk’s first win comes in 1953 at the Cairncastle hillclimb at the wheel of a VW Beetle. He is offered a free Beetle for the 1953 Circuit of Ireland by Isaac Agnew of Belfast. It is the first of many Circuit entries. The following year he leads the Circuit on the first day of the competition.
Hopkirk starts his winning career in professional racing and rally driving in 1955, taking a class win at that year’s Circuit of Ireland Rally, and clinching his first Hewison Trophy, awarded to the most successful Irish rally driver of the year. He goes on to win the Trophy for three consecutive years. By this time he has graduated to a Triumph TR2. His success in the Triumph is noticed by the Standard Motor Company, who offers him his first factory drive in a Standard Ten at the 1956 RAC Rally in March of that year, where he takes the early lead before suffering problems later on. Two months later he takes a Standard Eight to third place in the Tulip Rally in the Netherlands, his first trip outside of Britain and Ireland. However he loses his drive with Standard in 1958, after overdriving his car at the Alpine Rally in an effort to make up time lost due to a puncture on the Stelvio Pass, damaging the engine and forcing him to retire from the competition.
In 1959 Hopkirk joins the Rootes Group as a works driver, initially picking up a drive in a Hillman Husky at the Safari Rally after reigning F1 World Champion Mike Hawthorn, who is originally meant to drive the car, is killed in a road accident. Later that year he places third overall and takes a class win at the Alpine Rally in a Sunbeam Rapier, and he leads the 1960 Safari Rally until his Rapier suffers a differential failure. He takes two Circuit of Ireland Rally wins in 1961 and 1962 and another third at the Alpine Rally in 1961. While at Rootes he also takes part in circuit racing, winning his class in a Rapier in the touring car race supporting the 1960 British Grand Prix.
Hopkirk finishes third at the 1962 Monte Carlo Rally in a Sunbeam Rapier. However, he becomes frustrated by the Rapier’s lack of reliability, culminating in all three works cars blowing their engines within the space of a kilometre at that year’s Acropolis Rally. After being impressed by a test drive of Pat Moss‘ Austin-Healey 3000, he sets his mind on a move, joining the British Motor Corporation and making his debut in a 3000 at the Liège-Sofia-Liège rally in August. In his second competition with the 3000, the RAC Rally, he finishes in second despite having to complete two miles of a special stage with a shredded tyre after a puncture. He first competes in a Mini at the 1963 Monte Carlo Rally, where he finishes sixth. That season he also finishes second on the Tulip Rally, sixth on Liège-Sofia-Liège, and fourth on the RAC Rally. In addition he takes the Mini to third place in the Tour de France Automobile‘s Touring Category behind two 3.8-litre Jaguars, winning his class and the overall on handicap.
Alongside Henry Liddon Hopkirk wins the 1964 Monte Carlo Rally in a Mini Cooper S. They are the most recent all-British crew to have won the event. He also leads BMC to the team win, with fellow Mini drivers Timo Mäkinen and Rauno Aaltonen pacing fourth and seventh. The victory makes him a household name. He receives telegrams from the then UK Prime Minister Alec Douglas-Home and the Beatles, is given the Freedom of the City of Belfast, and appears along with his Mini on Sunday Night at the London Palladium. He goes on to steer an Austin-Healey to victory at his next international rally, the Österreichische Alpenfahrt, later that year.
Hopkirk also travels to Australia during his career to drive for the BMC Works Team in the annual Bathurst 500 race for standard production cars at the Mount Panorama Circuit. He drives at Bathurst in a Morris Cooper S from 1965 to 1967, obtaining a best result of 6th outright and 3rd in class in the 1965 Armstrong 500 when paired with Mäkinen. In 1965, he wins a Coupe d’Argent at the Alpine Rally. He wins the 1965 and 1967 Circuit of Ireland Rally, the 1966 and 1967 Alpine Rally, and the 1967 Rally Acropolis.
In 1968 Hopkirk finishes second at the second edition of the Rally de Portugal. The following year, he finishes second in the Circuit of Ireland Rally and the RAC Rally, then fourth at the 1970 London to Mexico World Cup Rally with teammates Tom Nash and Neville Johnston in a Triumph 2.5 PI. He elects to step away from full-time competition at the end of that year, coinciding with British Leyland head Lord Stokes‘ decision to close down BL’s competition department.
In 1977, with co-driver Taylor Mike, Hopkirk takes part once again in a revived edition of the London-Sydney Marathon, the Singapore Airlines London to Sydney Rally, this time driving a Citroën CX 2400, taking third place overall in front of another CX driven by Claude Laurent and Jean-Claude Ogier.
In 1982, Hopkirk wins the RAC Golden 50, a historical anniversary race celebrating the 50th RAC Rally, with co-driver Brian Culcheth in the Mini Cooper with which Timo Mäkinen had won the 1965 Monte Carlo Rally. In 1990, he wins the Pirelli Classic Marathon with co-driver Alec Poole. In 1994, he enters the Monte Carlo Rally again, driving a current Mini Cooper, very similar to the original car, but now produced by Rover Group. He and his co-pilot Ron Crellin finish the race in 60th place against much more modern and powerful machines.