But the young Brit, speaking at the Autosport International show on Saturday, believes it is the right career move towards his long-term ambition of racing in Formula 1.

"Definitely F1 is my goal and has been since I started racing when I was 10 years old," said Green, a former McLaren Autosport Young Driver of the Year. "But being a part of the Mercedes team in the DTM is a very professional level to be racing at - I'm sure I'll learn a lot and I believe it's a step forward from Formula 3, albeit in a slightly different direction.

"With the competition we have in DTM with the ex-Formula 1 guys and the young guys like Gary [Paffett] and [Mattias] Ekstrom, there's a good mix of talent and I think there's a lot the young guys can learn. So I think it's a good school to be in, and the cars aren't so different from a single-seater, and hopefully that can be good experience I can carry forward into Formula 1 if I get the chance."

Another factor in his decision was the fact that he would have had to bring personal sponsorship to the table to compete in GP2 (nee Formula 3000), a constraint that does not apply to the works Mercedes DTM team.

"Financially it was the best thing for me to do," confirmed Green. "To find the budget to do GP2 is very difficult and maybe you need to do two years there. I've been fortunate enough to have a good budget to race for competitive teams for the last three years. In the DTM it's another way round - you get paid a wage, and I believe I'm still going in the right direction to get into Formula 1."

Green says he doesn't expect the transition from a lightweight single-seater to a flame-spitting 500 bhp touring car to pose any particular problems for him, but having sampled the Mercedes C-Class in a three-day test he found he liked what he saw.

"It's a fun car to drive - it's very quick in a straight line, the braking is very impressive and it has good mechanical grip. It doesn't have as much downforce as an F3 car, so it's not quite as good in the high-speed corners. Physically it's probably about the same - less G-force in the quick stuff but more under braking and acceleration, and of course the cockpit conditions are very hot.

"There's enough power that you have to take care of the rear tyres when you accelerate out of slow corners, but although it's high-tech for a touring car you really have to drive the cars yourself, and there's no traction control or ABS brakes these days."