Revised again in 1979, the Series II had, said Dymock, "only a sleeker roofline and detail changes to the windows to show that some £7million had been spent in retooling and improving it". Some of that £7million had gone on the services of Italian design house Pininfarina, the first time Jaguar had out-sourced any styling work. This wouldn't have happened under Lyons, said the pundits. In effect, the exterior re-touching amounted to little more than a lowered waistline and more headroom, though in retrospect, the Series III is still a very attractive car, and it was better that it did not go over-angular like many cars of the time. Pininfarina was generally considered to have made a fine job of the facelift, but Jaguar made a mess of the launch - huge problems with company's new paint plant meant that it could only paint Series IIIs in three colours for months after the launch, which is why plenty of W reg XJs are white, yellow or red.

The entry-level 3.4 (with cloth upholstery) and 4.2 versions continued, but all now had electronic ignition; the 4.2 gained fuel injection. Economy was hardly improved, though, and Jaguar had to revise the gearing to make the 3.4 significantly more frugal than the 4.2. The XJ12 engine was more comprehensively revised, receiving a double combustion chamber integrated into the cylinder head, electronic ignition and new Lucas digital fuel injection. It now had a badge 'HE' - High Efficiency - which was a bit of a misnomer considering it now did all of 15-21.5 mpg. But, it was undeniably an improvement.