I've just learnt that the XJ40 model of the Jaguar XJ didn't get the V12 engine until 1993 (not sure exactly when in that year, though). Before that I think they continued to sell the old XJ12 (Series III) alongside the new XJ40 XJ6. So all XJ40s made before 1993 will definetely be XJ6s. So if an XJ40 appears in a pre-1993 movie or carries a UK numberplate with a letter below L (and possibly K) is definetely an XJ6. The XJ40 XJ12 was only produced for two years (1993-94). The next XJ12 (for the X300 model Jaguar, technically the 6 litre V12 version was the X305) was released in 1995 and was also only made for two years before Jaguar did away with the V12 engine altogther and introduced the V8-engined X308 XJ8 in 1997. The X300 (or X305) XJ12 had a V12 badge on the central door pillar. Also the XJ40 XJ12 was technically called the XJ81, but we can still keep grouping under XJ40.