Driven by Victor Harman and David Hancock, the Leon achieved an average consumption of 66.38 mpg on the 340-mile course, which was completed at ‘around 36 mph… quicker than most, if not all, the other competitors,’ according to Harman. 

The result was enough to bag the Leon a win in the Class 4 category, for diesel passenger cars with CO2 emissions between 110 and 180 g/km. It is a 3.39% improvement on the car's 64.2mpg official combined rating – and was achieved with a standard specification car, on standard tyres. 

In response, Harman has issued tips for drivers on how to make sure they're driving as efficiently as possible:

The Leon SC FR TDI 150 PS DSG that the pair were driving comes as standard with SEAT Drive Profile, which not only offers a Sport mode for a more engaging driving experience, but an Eco mode that encourages a more economical driving style and a Comfort mode.

The SEAT Leon is priced from £15,550 for an SC model in S specification with a 1.2 TSI 104bhp petrol engine. The three-door FR 2.0 TDI 150PS DSG that competed in the MPG Marathon is priced at £22,515 OTR.