Mr Dewis, chief test driver and development engineer for Jaguar Cars from 1952 to 1985, will be taking in this year’s MPG Marathon at the age of 95.
He will be entering this year’s event, considered to be the UK’s leading lean-driving challenge, in a 2.0-litre 163hp Jaguar XE, alongside Jaguar Heritage communications officer Tony O’Keeffe.
Over the years Mr Dewis has played a major role in the development of some of Jaguar’s most iconic models, including the E-Type, XJ6, XJ-S and many more.
He was also behind the wheel of a Jaguar XK120 in October 1953 when it reached 172.412mph at Jabbeke in Belgium, a record for production cars at the time.
Awarded the OBE for services to the motor industry in the New Year’s Honours List at the start of this year, Mr Dewis has become an unofficial ambassador for Jaguar - regularly attending events and giving talks about his work for the company.
Event organiser and Fleet World publishing director, Jerry Ramsdale, said: “We are delighted Norman Dewis has entered this year’s MPG Marathon as our oldest ever entrant.
“It will be great to see how such a driving legend, famed for his high speed driving exploits, copes with the demands of driving as frugally and as economically as possible in one today’s most modern cars.”
This year’s MPG Marathon, which takes place on September 29 and 30 and is now in its 15th year, sets off from the Heythrop Park Hotel near Enstone in Oxfordshire.
Along with Jaguar car-makers entering include BMW, Caterham, Ford, Peugeot, Renault, Citroen, Honda, Mazda and Kia.
This year’s event allows competitors to find the most efficient route between set checkpoints for themselves, taking into consideration possible congestion hotspots, such as town centres.
Electric and hybrid vehicle classes will also be included, joining the more familiar diesel and petrol engined cars and vans that traditionally take part in the event.
There are eight main classes of passenger cars, restricted to a maximum carbon ceiling of 190g/km, including hybrid, range-extender and fully electric vehicles, plus five main classes of vans.