One of the revisions is the use of the second generation of Jaguar's independent rear suspension unit, taken from the Jaguar XJ (XJ40). Development began in 1992, with design work starting earlier in late 1991. By October 1992 a design was chosen and later frozen for production in 1993. Prototypes were built from December 1993 after the X100 was given formal approval and design patents were filed in June 1994. Development concluded in 1996, with the car being unveiled in March of that year and going on sale from October 1996.