I hold my brother-in-law wholly responsible for turning a sensible, straightforward day trip into a mileage marathon.

The plan was simple. Leave at 8am, spend the day at the Black Country Living Museum in Dudley and be home for tea.

But as we headed north he looked out of the window at the unseasonably bright winter sunshine and cloudless blue sky and said: “On a day like this we should be at the beach.”

Within minutes the car was heading towards the southbound M5 and we arrived at Porthcawl, in South Wales, in time for lunch.

We finally arrived home at 8pm having clocked up 400 miles – and I could not have felt fresher, thanks entirely to the grand tourer that whisked us around.

Solid, superbly built and unflappable, BMW’s 5 Series remains a hugely important pillar of the German carmaker’s business. With more than two million sold and the car remaining stubbornly at the top of expert and reader polls the 5 Series can justifiably claim to be the world’s most successful business car.

Our test car started life with a price tag nudging £39,000, but add a selection of packages – technology, comfort and M Sport Plus – and the car rolls out at more than £48,000.

But what a car it is. Press the starter button and the 2.0-litre engine burbles into life. It’s a diesel, but I challenge anyone to tell that once the car starts sailing upwards through the eight-speed automatic gearbox.

Riding on huge 19-inch alloy wheels, the four-door saloon is surprisingly nimble considering its impressive size. Whisper quiet, the driver and front seat passenger are ensconced in supremely comfortable leather-trimmed sports seats, with a host of technology at your fingertips and a Harman Kardon surround sound system to help pass the time.

Part of the technology package is a superb colour head-up display that relays not only speed and satellite navigation directions to the driver, but information from the hi-fi system and Bluetooth mobile phone link.

This car is packed with equipment but it is typically understated and in no way intrusive. The electrically-operated driver’s seat has memory settings which adjust not only the seat and mirrors, but also return the multi-function steering wheel to its pre-set position. The large exterior mirrors fold in automatically as the car is locked.

At low speeds, the combination of radar-operated sensors and a reversing camera make parking this large car a real breeze.

The claimed combined fuel consumption is a mighty 65.7mpg though I never got close, registering about 50mpg in my time with the car, but even this is sufficient to deliver a full tank cruising range of more than 700 miles

Though we will not be travelling by BMW next time, tickets to the Black Country museum have been purchased and it is next on the list to visit. Weather permitting…

Auto facts

Model: BMW 520d M Sport saloon

Price: £48,495 as tested

Insurance group: 31 (1-50)

Fuel consumption (combined): 65.7mpg

Top speed: 146mph

Length: 493.6cm/194.3in

Width: 186.8cm/73.5in

Luggage capacity: 18.7 cu ft

Fuel tank capacity: 14.5 gallons/66 litres

CO2 emissions: 114 g/km

Warranty: Three years/ 100,000 miles