When the Banglefied BMW 7-series was unveiled, hushed gasps were clearly audible. BMW showrooms across the land later echoed to this same sharp intake of breath, as interested tyre-kickers walked to the rear of the plutobarge and saw the protuberance that is the boot-lid.

The 5-series, however, is a car the blue and white propeller can’t afford to screw up.

Not only is it a big seller in its own right, but as part of the aspirational heartland of the Bavarian brand, 3-series owning reps thrusting their way up and down our motorway network need something to work towards.

So is this latest incarnation of the new-fangled Bangle the stuff of dreams or nightmares?

Breathe a sigh of relief at the rear, as the 5-series bottom doesn’t look like a baboon’s arse. One might even go so far as to call it contemporary. It’s clearly a Five from the rear, even without the badging.

There are the classic BMW styling cues such as the Hoffmeister kink to the rear window line, and the best implementation of Bangle’s “flame-surfacing” on the doors and lower sills we’ve seen so far.

Things are more awkward at the front, however, particularly at the A-pillar where door, windscreen and front wing meet in an uncomfortable assortment of panel gaps, shut lines, and ridges. It’s not a glaring issue, but it’s clearly an area that could have been better resolved.

We’re not a fan of the new-style kidney grille which, with each new model, looks increasingly like a pair of nostrils more at home on a Renault. However, we’re pleased to see the Mysteron headlights have been carried over from the previous Five, and even the new eyebrow treatment doesn’t look out of place.

BMWs have always been sold and thought of as a quality product. The Ultimate Driving Machine mantra implies engineering excellence in all components of the vehicle.

It’s a shock, then, when you reach to open the driver’s door for the first time.

It feels cheap. There’s a crunchy, ratchety action to the hollow-feeling door handle that wouldn’t feel out of place on last year’s best-selling Korean super-mini. As this is likely to be the first interaction prospective Bimmer owners have with the car, it’s not a good start. Showroom appeal – nil point.

While most criticism of Chris Bangle’s new design language has been levied at the exterior, we can’t help feeling that the interior is where he’s done the most damage.

BMWs of a generation or two ago had centre consoles beautifully angled towards the driver – Ultimate Driving Machine, remember – but today the dashboard runs from one side of the cabin to the other in a wide strip. In truth, it’s not unlike sitting behind a desk.

The instruments appear too small in comparison to the rest of the dashboard, but they are at least clear and easy to read.

The column stalks will no doubt prove to be a source of frustration for many. The indicator stalk is an almost exact replica of that used for the cruise control just below it, and both are labelled with up and down arrows. The stalks are too short for comfortable use and someone in BMW appears to have driven a Vauxhall Vectra recently. When you activate an indication in a particular direction, the stalk returns to its usual position but the indicator remains on, cancelling electronically when you turn the wheel in the opposite direction. At first, it’s unnatural, but it quickly becomes annoying as the system cancels incorrectly when negotiating right-hand turns at roundabouts.

The steering column itself adjusts for reach and rake, although not by enough in any one axis. The optional electrically adjustable column appears to limit travel further, retracting slightly as you move the column downwards.

The quality of plastics aren’t up to usual BMW standards – the rotary temperature controls feel cheap to use, as if lubricated by grit, and pressing any of the climate control buttons sees the flimsy panel they’re mounted to bow disconcertingly. The central armrest, with its pop-open compartments, creaks and springs open like a child’s toy.

Much has been written about BMW’s iDrive and we’re not about to add to that. We will say, however, that we find it bemusing that BMW should invest in a Heads-Up Display for the satellite navigation system to keep drivers’ eyes on the road, only to negate that good work by fitting a control system that forces drivers into a squint-and-twiddle search for Radio 2.

The seats have a strange lumbar support in the backrest that couldn’t be adjusted out in our test car, and the discomfort was added to by the internal door handle that runs exactly where the driver’s right knee wants to be. It’s hard, with sharp corners, too. There’s not enough aft travel on the seat runners for tall drivers, either.

Disappointingly, this all adds up to a feeling of discomfort and confinement, and you have to wonder where BMW spent all the money.

You soon find out when you turn the key. The 3.0-litre straight six diesel unit purrs to the tune of 218bhp and 369lb/ft of torque peaking right where it should do – at a lowly 2,000 rpm. From inside, you wouldn’t know you’re in a derv-drinker once the engine has been running for just a few seconds, and even on the move and under power, there’s very little to give it away other than the characteristic shove towards the horizon.

The torquey power delivery suits, in our opinion, the six-speed automatic gearbox perfectly. Drivers can choose between a typical point-and-squirt style or use the Tiptronic function to change their own gears. The auto ‘box doesn’t blunt performance noticeably, either, with a 0-62mph time of 7.3 seconds that’s only 0.2 seconds slower than the manual car. Top speed is only one mph down at 151 mph. Economy takes a bigger hit, however, averaging 36.2 mpg on the combined cycle versus 40.9 mpg for the manual. Emissions might concern company car drivers, with CO2 figures of 184 and 208 g/Km for the manual and self-shifting versions respectively.

Whichever gearbox you choose, you have to wonder why anyone would buy the 3.0-litre petrol model. The two units are comparable on power, with only 13 bhp between them, while the diesel produces 150lb/ft more torque 1,500 rpm lower down the rev range, and has better emissions and superior economy. The performance figures are almost identical, too, with the exception of the 530d’s incredible overtaking lunge.

On the road, things make even more sense. There’s a quality to the ride and a degree of body composure that’s so obviously missing from many of its rivals. Even at low speeds, seams in the tarmac are prevented from making an audible appearance in the cabin, and even cat’s eyes are downgraded to a distant ‘wub’. We’re not sure the optional Sports suspension is necessary or worth it.

Rapid changes of direction fail to upset the body, and the added weight of the diesel engine up-front doesn’t spoil steering response or feel. We wondered if the increased mass may actually have improved things.

As long as you leave the expensive Active Steering on the options list, there’s plenty of feedback available through the wheel, and never any doubt as to whether the front wheels will obey the helm’s inputs.

Cornering grip seems almost limitless within the confines of the public roads, and even with the suspension heavily compressed during enthusiastic cornering, bumps fail to divert you from your chosen line.

The 530d SE has an on-the-road price of £31,900. Standard spec includes 16-inch alloy wheels, remote locking, ABS, DSC, rain-sensing wipers, air conditioning, iDrive with 6.5-inch colour display, cruise control, all-round electric windows, single-slot CD player, park distance control and metallic paint.

As you’d expect of a BMW, there’s a commodious list of options, seemingly tied together in a clever marketing trick to inflate your chosen car’s sticker price. Satellite navigation, for instance, is available in two distinct flavours – if you’d like a map with your fries, you’ll need the more expensive Professional version (£1,650 please), which also demands that you spend £575 on the upgraded climate control (why?) and, as you’ll lose the ability to play audio CDs while navigating, you’ll need to fork out an additional £270 on a CD changer.

All told, our test car totalled out at £36,995 after adding sat nav, leather seats, and auto transmission.

Insurance is higher than many of its rivals at group 17, although servicing costs over three years are predicted to be lower than most of its peers. At the end of the three-year warranty period, the 530d will have held on to 54% of its value, assuming a mileage of 60,000.

So, the ultimate driving machine, then? There’s no questioning the excellence of the engine, gearbox and chassis, all of which can be referred to as ‘class-leading’. The exterior styling is the most cohesive of the current BMW range, despite the best efforts of The Bangle.

But that interior. It feels cheap, messy and uncomfortable. We’re not sure we can forgive it for that.

Brilliant engine – why would anyone buy its petrol brother? Fantastic chassis – truly, the class leader. But that interior – seemingly engineered down to a price, with quite shockingly poor ergonomics for a company that used to lead the market. iDrive still a solution to a problem that doesn’t exist.
Our verdict: Our verdict: 3.5 stars out of 5