There is a sure fire way of finding out if your car is well built.

Never mind the quality of the materials or the delicate stitching on the seats and door cards.

Take it through a car wash, open the doors and boot and if there is no sign of drips the job’s a good ’un.

I put the BMW 5 Series to the car wash test and it passed with flying colours. Not a drop to be seen, and to round it all off the cabin trim is spot on as well.

We have been lauding BMW’s premium executive saloon for four decades and it is fair to say this latest model is probably as good as it gets.

Has there ever been a bad 5 Series? Well, the rear end grip on the early models was iffy, and the first attempt with the iDrive system needed a brain like Einstein to work it, but really, this is scrabbling for faults.

It has been a favourite in the executive parking spaces for 46 years, and a thorn in the side of the Mercedes E-Class and Audi A5.

In truth there is only a hair’s breadth between them and we can add the wonderful Jaguar XF to the ‘special ones’. Phew, choosing between Five and a Jag is a difficult one.

So what has been going on with the Beemer? Not a lot, it doesn’t look a lot different, just a few nips and tucks here and there to keep it fresh, although something that does stand out is the improved level of comfort even on broken surfaces.

Even that is an oddity as this is an M Sport which means stiffer suspension and everything else that allows the car to tear round a track.

No need for concern because the level of suspension travel can be changed at the push of a button. Even more surprising is the subtlety of the ride in sport mode. It is not bone crushingly hard and still allows you to have some fun.

That said there is plenty of enjoyment in comfort mode. It is a car that can be driven quickly but calmly with steering that is quick and pin-point accurate.

My only question is why would you buy an M Sport model with a 2-litre diesel under the bonnet?

We don’t want to get too carried away but this is one hell of a diesel engine and you don’t need the expense of the M Sport to get it.

Far better to go down a couple of pegs and put an extra grand to the variable damper control system and you have it all.

It is not a new engine but is well muffled and can be barely heard even cruising the motorway. With the eight-speed automatic 70mph requires an improbable 1,600rpm, and if you do ramp it up to a modest 3,000rpm in top you have seriously broken the speed limit.

Inside feels special, lots of high quality materials, beautifully put together, and a clearly laid out dashboard with clear digital dials in the binnacle. It does not have the dramatic visual impact of the Merc E Class but then nothing comes close to that stunning interpretation.

At least the iDrive is gremlin free. The screen sits proud taking centre stage with a dial behind the gear lever operating a comprehensive cast list. It looks daunting but is quickly learned.

As with all the premium brands a lot of what you want can be found in the options list and the 5 Series is no exception.

Packs can cost anything from £1,500 to all but £2,000 along with individual items. I was disappointed to find the head up display (that will be a standard fit one day) is an extra on this model, along with a reversing camera, part of the comfort pack.

I would certainly pay £335 for split folding rear seats which extends boot capacity.

BMW has covered all bases combining comfort, quality, performance, economy, and, above all, sheer driving pleasure.

Ultimately there is very little between the top four apart from that little spark that singles one out. The 5 Series has that spark.

BMW 520d M Sport

Engine: 1995cc diesel; 190bhp
Performance: 0-62mph 7.5secs; 146mph
Economy: 68.1mpg combined
Emissions: 114g/km. Road tax £140
Insurance group: 31
Price: £39,025 (£48,495 as tested)