Following the success of the Riley & Scott MK III, the company began work on a new chassis. In North American sports car racing, the MK III won more than 60 races, seven driver championships, and three Rolex 24 at Daytona victories.

The Riley & Scott MK XI was designed to compete in the Rolex Sports Car Series Daytona Prototype class beginning in 2003. The new car incorporated design elements from the MK III. It was given a steel tube/aluminum reinforced chassis and clothed in an aerodynamic body. The vehicle was designed to house any class-eligible motor. Interested recipients of the car were able to take possession of the new car in the fall of 2002, in time for testing for the 2003 Rolex 24 at Daytona.

'The response we have received since the announcement of the Daytona Prototypes only three weeks ago has been remarkable. There has been overwhelming interest in the new Daytona Prototypes,' Grand American Road Racing Association President Roger Edmondson said. 'We consulted with Riley & Scott during the early planning stages of the Daytona Prototypes because of their impressive history of sports car manufacturing. Just as the Riley & Scott Mk III has been a leader in the Sports Racing Prototype class, I am confident the Mk XI will be a venerable competitor in the new Daytona Prototypes class.'

Only one Aston Martin-powered Daytona Prototype was produced.

In 2004, Chip Ganassi Racing won the Grand-Am championship using their Lexus-powered Riley MK XI. The Manufacturers Championship went to Riley in 2004, thanks mostly due to the Chip Ganassi & Sun Trust Racing teams.

by Dan Vaughan