It broke its rear axle in the paddock at its first meeting, but buying spare parts for the Bugatti was too expensive, so it was replaced with a MG Magnette K3.

Meanwhile, he started to construct his own car for voiturette (the pre-war version of Formula Two), known as the Challenger, however with the outbreak of World War II, the best years of his career were wasted.

[6][7] During the war years, Parnell finished the Challenger and built up a comprehensive collection of racing machinery, which included Alfa Romeo, ERA, Riley, Delage, MG and Maserati models.

This proved to be a poor year for mechanical reliability, although in his Maserati 4CLM, he did finish second behind Prince Bira in the Ulster Trophy, around the streets of Dundrod.

He won the Goodwood Trophy at the first-ever meeting at Sussex circuit, was second in the Penya Rhin Grand Prix and fifth in the Gran Premio d'Italia.

When he arrived at the race, the lead French driver, Raymond Sommer immediately objected but Parnell had checked the rules beforehand and found that there was nothing to preclude twin rear wheels.

He left a star-studded field standing in conditions so bad that the BRDC International Trophy final raced through hail, lightning and heavy rain.

With poor visibility and the track under as much as six inches of water, the race had to be stopped after six laps due to Silverstone being flooded and too dangerous to continue.

[6][7][10] At the Grand Prix de l'A.C.F., BRM announced they would race at Reims-Gueux with Parnell, so Vandervell offered the Thinwall Special to Brian Shawe-Taylor.

[8] Following his success into the 1950 RAC British Grand Prix, Parnell was signed by Aston Martin, taking a DB2 to sixth place in to 24 Heures du Mans, partnered by Charles Brackenbury (second in class).

[6][11] In 1952, Parnell enjoyed more class success with the DB2, taking wins at Silverstone and Boreham; at Goodwood, he unhesitatingly assumed duties as team manager for Aston Martin, following a pit fire seriously injured John Wyer.

At that year's Mille Miglia despite driving on the ignition switch after a broken throttle had to be wired up fully open, he and navigator, Louis Klemantaski finished in fifth place in their DB3.

[6] In 1954, in addition to his commitments for Aston Martin, Parnell continued to drive his own Ferrari 625 in numerous Formula One events, winning at Goodwood, Snetterton and Crystal Palace.

During 1956 Whit Monday at Crystal Palace, Parnell crashed Rob Walker's Connaught B-type, suffering a broken collar-bone and a badly cut knee.

During the 1961 Formula One season, he ran two Cooper T53 Low-Line–Climax cars for John Surtees and Roy Salvadori, who between them collected a handful of championship points.

For the 1962 season the team was renamed Bowmaker-Yeoman Racing, and in place of the Coopers, ran Lola Mk4 chassis, again powered by Climax engines.

During the season he also gave Parnell his first podium finishes as manager – with second places in both the British and German events – and took pole position at the season-opening Dutch Grand Prix.

Reg Parnell Racing was still in the early stages of development in its premises in Hounslow, running a car of the young driver, Chris Amon.

[5] Dr. Bartrip wrote that Parnell "could prepare a car meticulously and was as astute judge of a driver, identifying the potential of such talented prospects as John Surtees, Chris Amon, and Mike Hailwood".

Parnell's son Tim, also a racing driver, took over the team management and developed a strong working relationship with BRM during the late 1960s.