A record-breaking British car from the 'tween-war years has broken another record at the Bonhams Goodwood Festival of Speed sale this Friday 29 June. It is now the most expensive Bentley ever sold at public auction.

The ex-Sir Henry 'Tim' Birkin 1929 4½-liter supercharged 'Blower' Bentley single-seater, which when new raised the Brooklands Outer Circuit record to 137mph, sold for £5,042,000.

The Bentley was sold as part of a collection once owned by famed watchmaker George Daniels of seven cars, two motorcycles and assorted automobilia.

Daniels was a huge fan of Birkin, and also on sale at the Bonhams Goodwood FOS sale was another Birkin car. The 1932 Alfa Romeo 8C-2300 Long Chassis Touring Spider which formed part of Birkin's 1932 Le Mans 24-Hour Endurance Race entry with his friend Earl Howe, sold for more than £2.5 million.

Malcolm Barber, Bonhams chief executive officer and auctioneer at the Daniels sale, said: "The prices achieved for George Daniels's cars today are a fitting tribute to one of the truly great artist engineers of the 20th Century.

"George was not only a fantastic craftsman who hand-made some of the world's most desirable watches, he was also a car connoisseur held in immense respect throughout the vintage motoring world."

Doug Nye, Bonhams historian, said: "It is wonderful to see this iconic car's true appraise recognized by the world market.

"The Birkin single-seater Bentley was, in effect, the Concorde of its time, the fastest car around the high Brooklands bankings. It was driven by a great British hero in Sir Henry Birkin and was the most glamorous racing car of the era."

The 'Birkin' Bentley represents both an incredible piece of British racing and engineering heritage, and a remarkable achievement, both of which came about through the participation in a racing project of four top British personalities of the day.

First there was the fearless and charismatic aristocrat who was behind the wheel for the record lap. Sir Henry 'Tim' Birkin was a Baronet who became one of the most famed of the legendary 'Bentley Boys' of the 1920s – 30s. For an entire generation of British motor racing enthusiasts the mustached 'Tiger Tim' in his goggles, wind cap and polka-dot scarf was the epitome of Imperial power, speed and daring – a very British kind of hero. Intensely competitive, he was a born sportsman who raced for racing's sake and was whole-heartedly committed to making the most of his natural talent.

The engineering might behind the record effort came initially from Bentley founder and legend of his time, W O Bentley. Bentley's cars were designed with the motto: "To build a good car, a fast car, the best in class", and indeed they won the Le Mans 24-Hour Endurance Race on a number of occasions and set many records at the French track. Although the supercharged 'Blower' version was developed by Birkin with the backing of his financiers, it was based on the original 1927 design by W O, albeit against his wishes.

Despite the input of these two British legends in their fields, the success of the Birkin Bentley would not have been possible without the significant financial input of two of Britain's wealthiest people at the time.

Dorothy Paget, the daughter of Lord Queenborough, was a British racehorse owner who came from a prominent family of Thoroughbred racers and breeders. Her horses won a total of 1,532 races in both flat and hurdling, including seven Cheltenham Gold Cups and a Grand National in 1934. Living for the most part in Buckinghamshire and reportedly as eccentric as she was rich, she is said to have hated the sight of men – claiming they made her feel physically sick – and to have called all her staff by different colors rather than their names, apart from green, which she also disliked.

British financier and racing driver Joel Woolf 'Babe' Barnato was, like Birkin, one of the 'Bentley Boys', and he achieved three consecutive wins out of three entries at Le Mans. A product of Charterhouse School and Trinity College Cambridge, Barnato played cricket for Surrey in the late 1920s and served in the British Army and RAF during the wars. After inheriting his family's fortune, made out of diamond and gold mining in South Africa, he poured cash into the troubled Bentley brand, pushing through in the meantime the famous 'Blower' Bentley so disliked by W O.

These four remarkable personalities combined to produce a monster of a car that proved a real match for the aging, patched, bumpy and frost-heaved Brooklands circuit, a circuit Birkin himself described as: "...without exception the most out-of-date, inadequate and dangerous track in the world... Brooklands was built for speeds of no greater than 120mph, and for anyone to go over 130... is to court disaster... The surface is abominable. There are bumps which jolt the driver up and down in his seat and make the car leave the road and travel through the air."

Following its race career, the car was converted into a two-seater roadster before being acquired by George Daniels.

Daniels was one of the few modern watchmakers who could conceive, design and hand-make a complete watch from blank sheet of paper to finished timepiece. During his lifetime he created fewer than 100 pocket watches and wristwatches, each of which would typically involved 2,500 hours of work. Awarded a CBE in 2010, he is the only watchmaker ever to receive the honor 'Master Watchmaker, for services to Horology'.