Herbert Mackay Fraser was born either in Connecticut or according to some sources, Pernambuco, Recife in Brazil. He was the son of an American businessman who owned a coffee plantation in Brazil. He was an accomplished downhill and slalom skier and he used his balance and rhythm in his driving.
Mac tried his hand at ranching in Wyoming before moving to California, which is where he started racing with an XK120 Jaguar. He moved back to Brazil settling in Rio de Janeiro. He continued racing, competing in national events with a Ferrari 750 Monza.
However Mac wanted to race in Europe and in June 1955 he traveled to Portugal and at the end of the year to London. He became close friends with Jo Bonnier and together they competed in European sports car events traveling in an old black and yellow bus with the words Scuderia Bonnier painted on the side. Mac raced his own Ferrari Monza under the 'Kangaroo Stable' banner and also drove Bonnier's Maserati on occasions.
Settling in London, he soon integrated himself into the British motor racing scene, driving for Colin Chapman's fledgling sports car team racing in small-capacity sports cars in 1956 and 1957. Driving in the UK and taking in a number of races on the Continent in his own Ferrari and Bonnier's Maserati during 1956, he really made a name for himself in the Reims 12-hour race, which he led superbly in Bueb's Lotus until engine troubles intervened.
In 1957 he continued his successful association with Lotus and made his Grand Prix debut for BRM at the 1957 French Grand Prix at Rouen a fortnight after his 30th birthday. Standing in for Roy Salvadori when he switched to Vanwall. Vanwall's drivers, Stirling Moss and Tony Brooks, were both out of action: Moss with a sinus infection and Brooks as a result of a crash at Le Mans. Mackay-Fraser was running sixth behind the Maseratis and the Lancia-Ferraris for the first part of the race when his transmission failed. It had been a very promising F1 debut.
A week later he went to Reims for the F2 Coupe Internationale de Vitesse. Lotus had entered three cars, two new Lotus 12 for Cliff Allison and Colin Chapman and an older stripped down Lotus 11 Le Mans car for Mac.
Salvadori lead at the start, with Brabham and Trintignant right behind. Reims favored slipstreaming that ensured much swapping of positions. Unfortunately on the second lap Bill Whitehouse crashed at the approach to the Thillois hairpin. With multiple fractures and serious burns, Whitehouse was taken by helicopter to the Centre Hospitalier de Reims. Meanwhile in the lead Trintignant and Salvadori swapped places several times every lap. The Cooper was quicker in a straight line while the Ferrari was better in the corners. On the tenth lap they crossed the line side-by-side. Brabham was third a few seconds back followed by Jean Lucas, driving Alan Brown's Cooper, another 14 seconds down the road with Tony Marsh in a similar car right on his tail. Frazer was sixth, five and a half seconds behind Lucas and Marsh. Only nine cars were still on the lead lap.
A few laps later Brabham upped his pace and overtook Trintignant and closed in on Salvadori. Roy responded with a new lap record on lap twenty. By then the three leaders had opened a gap of almost two minutes over Lucas, who in turn had managed to break clear of Marsh. Mac struggled to keep up and was more than fourteen seconds behind Marsh when he crashed at high speed and was killed, becoming the first fatality for the factory Lotus team.
Brabham and Salvadori both retired leaving Trintignant to take the win. Bonnier won the sports car supporting race but the death of his friend ensured that there were no celebrations that weekend.