They're currently crossing the Ts and dotting the Is on the new Jaguar XJ, ready for the start of production in November.
The car is 99.9% finished, but there are still bits and pieces that need improving, and there's fine-tuning to be done on the shock absorbing and steering.
Cars might be designed and engineered 'virtually' on computer these days every facet of their crashworthiness and dynamic behaviour is accessible at the click of a mouse but the human touch still counts when it comes to finalising some things.
Mike Cross, Jaguar's chief development driver, leads the team that's responsible for how Jags drive and they've been doing a pretty sound job this past five years or so.
Now they're trying to keep the winning run going with the new XJ and we've been out in it with Cross to observe, from the seat that would normally be occupied by a cabinet minister or captain of industry, how it's shaping up.
One of the first requirements with any new car is to define its character. 'The XK has to be our most extrovert car, the XJ the most refined and the XF somewhere in the middle,' says Cross.
'The roads that cars are developed on influence their character. We're very fortunate in the UK in having such a wide variety.
'We do our initial tuning in Warwickshire and then use the German autobahns for high-speed work and Wales for agility and precision.
Jaguar's aim with the XJ was to create something that blends the efficiency of the German opposition with the individuality of the Maserati Quattroporte.
'We're looking for duality,' says Cross. 'We want comfort and control; a car that is smooth and responsive all the time, but that allows the driver different ways to access that.'
Like its predecessor, the new XJ is made entirely of aluminium and other alloys to save weight, and is available in standard- and long-wheelbase (+125mm) formats.
However, the new car has air springs only at the rear rather than at all four corners, and it has a new form of continuously variable shock absorbing that gives the driver three set-up options.
'We've deliberately ensured the differences are subtle,' says Cross, 'and anyway, when you're tramping on the dampers react really quickly, regardless.'
Tramping on is certainly an apt description of the pace of our ride in Snowdonia, yet from the back of the long-wheelbase 5.0-litre supercharged V8 Cross brought along, it was all so quiet; so unruffled.
View from the back
Rear seats aren't always the ideal place to experience a car's refinement and ride at its best. Rear suspension noise (and bumps) can easily make their way into the cabin if everything's not just so; a gentle breeze can sound like a gale.
None of this is an issue in the XJ. Cross is a softly spoken chap and the long-wheelbase car put some distance between him and us, yet we could hear every word of his answers to our questions.
Even the V8 engine is little more than background music, especially as it's now free of the old supercharger whine.
'We've tried to make it sound powerful, but refined powerful,' says Cross.
Most impressive of all is the car's body control. It makes the elaborately crafted grab-handles redundant. You can read or scribble notes on the move, even when 'tramping on'. And despite 20-inch wheels, you're rarely troubled by jolts.
You can only envy the people who'll soon be able to sit there every day. Even more, you can only envy blokes such as Cross who have already experienced the car from the best seat in the house.
Jag struck gold with the XF two years ago. It looks like it might have done it again.