On 31 March 1998, the XP5 prototype with a modified rev limiter set the Guinness World Record for the world's fastest production car, reaching 240.1 mph (386.4 km/h),[6] surpassing the modified Jaguar XJ220's 218.3 mph (351 km/h) record from 1993.

So 1993 to 1998 for the independently verified record.

McLaren's own test of the XP3 was in 1993 so it was really just waiting for that formality from that point on.