Dernie was brought up in Lancashire and educated at Kirkham Grammar School before he studied engineering at the Imperial College London university. Dernie was an apprentice with David Brown Ltd. His intention had been to get a job with Aston Martin since his ambition was to design racing cars. Whilst released from David Brown Ltd. as a student he managed to convince the University to let him do a 3rd year project to do with designing a racing car for himself, part of which ended up being a computer programme to optimise racing car suspension, which with the naivety of youth he did not realise had never been done before. By the time he left Uni to return to David Browns they had sold Aston Martin and he ended up as a junior engineer in the Noise and Vibration section of the R&D dept. Where he did a lot of measurements, including designing his own transducers. During this time he had met an engineer from March who had started using his software and therefore Dernie been analysing other engineering stuff for them, part time. He wanted to move a bit nearer the motor racing teams so looked for another noise and vibration job and got one at Garrard. He joined the Hesketh F1 team for, at the age of 26 designed his first Formula One racing car, the 308E. Dernie was the first racing car designer to develop software to aid Formula One car design. Frank Williams hired him to join Patrick Head at Williams in time to design the successful FW07 and FW08 cars. He also invented active suspension for use on the Williams car and developed their wind tunnel facility to improve aerodynamic development. He was the only person developing aerodynamics at Williams during this period. Dernie left Williams in 1988. For, Dernie joined Lotus, replacing Gérard Ducarouge as Technical Director. However, the team lost major sponsorship and were unable to fund essential R&D to make a competitive car. Ross Brawn, who had worked with Frank at Williams encouraged him to join Benetton for where he was instrumental in the development of the car, but in particular to improve the race team. At the start of 1992 Dernie was at the Ligier team during the tests where Alain Prost was evaluating the car, noting that he was around 1.5 to 2 seconds quicker than regular driver Boutsen could lap at. Dernie went to Ligier for the season to become technical director. He moved to Arrows for but only stayed for a year. Dernie left Formula One for the first time to join Lola in order to help the team re-establish itself in Champ Cars after MasterCard Lola's disastrous F1 foray in. In, Dernie left Lola to return to Williams as a consultant engineer in. He left in early and in August the same year joined the Toyota F1 team as a consultant in 'aerodynamic and chassis related matters.'
