a pair of Ultimo MK3 kit

Later, a pair of Ultimo MK3 kit car, the chassis numbers 12 and 13, “Albert” and “Edward”, the last two MK3s was regarded as "mules" to test various components and concepts before the first car built. Number 12 has been examining the gearbox with a 7.4 liter V8 Chevrolet to imitate the couple's BMW V12, and various other components such as seats and brakes. Number 13 the test of the V12 as well as exhaust and cooling system. At McLaren was destroyed by cars every two of them to keep away the magazines and because they do not want the car to be linked with "kit car".

The car was unveiled for the first time on a show starting May 28, 1991 was forced to change the car a at Sporting Club de Monaco. The production version has remained the same as the original prototype (XP1), with the exception of wings, the mirror in which XP1, was installed as head of the column A. This car has been regarded as non-legal route because there were no indicators on the front; McLarens a result (a few cars, including Ralph Lauren, have been returned to McLaren, with the prototype mirror). The first winged mirror of a couple indicators from other carmakers. A few years later to adopted.

The safety car levels have first been proved, if, in a test in Namibia April 1993, in a driving test contributes to shorts and T-shirt took a stone and rolled the first prototype car several occasions. The driver escaped unharmed. Later in the year, the second prototype (XP2) was built specifically for crash testing past, and without prejudice to the front Radiate.