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BMW is upping the ante with its plug-in hybrid technology - the 330e is proving a big success, the 530e will arrive next year, and the X5e, already on sale, became the first model from the firm to distribute its power permanently to all four wheels in electric-only mode.
So it was only a matter of time before the technology reached the firm's flagship car and it comes in two forms: the 740e and the 740Le xDrive. We drove the latter, a long-wheelbase version with all-wheel drive.
Still a driver's car?
As was the case with the 3-series plug-in, the addition of the hybrid system does little to dampen the overall driving experience of the 7-series.
It's just as smooth, comfort levels are exceptional, and despite the car's size and weight, feels nimble in the corners, while the steering offers plenty of feedback. Further traction is supplied from the xDrive all-wheel drive system, and because of the immediate torque available from the electric battery, the car's straight-line speed is seriously good.
Combined with the 112hp electric motor is a four-cylinder 2.0-litre petrol and together they produce 326hp and 500Nm of torque, capable of accelerating the luxury car from 0-62mph in just 5.3 seconds.
Like most of today's hybrids, there's a variety of modes available depending on how you want to use the battery. There's also an adaptive setting that utilises cameras and sensors to determine the right set-up.
As we've all come to expect from plug-in cars, CO2 emissions are significantly lower than your average diesel. This 7-series doesn't quite manage to squeeze under the 50g/km threshold, though - you'll need to avoid the xDrive system to achieve that, so tax costs are not quite as cheap as you may expect.
Tax bills are still almost halved in comparison with the 730d, however, which will cost a 40% payer £571 each month for the current tax year.
Officially 117.7mpg is indicated, although BMW expects a range of around 56-70mpg on an average 30-40 mile commute. If a BMW i Wallbox is fitted you can fully charge the battery from empty in as little as three hours for a 27-mile range of pure-electric driving.
It would take all day to talk about the sheer volume of advanced kit on this car.
You can buy the 7-series in three trims: Standard, Exclusive and M Sport, with the latter by far the most popular option in the UK.
As standard our test car costs £79,825, and kit highlights include high-quality leather upholstery, massage seats, four-zone climate control, sunroof, a reversing camera and ambient lighting.
There's a vast variety of impressive optional tech available too, from remote control parking and surround sound systems to gesture-control functionality and laser light headlamps, which double the reach of the beam. Get carried away and you'll soon push the price close to £100k.
The ideal chauffeur car
A lot of luxury chauffer companies will have their eye on this car as a prospective addition to their fleets and, as well as the tax benefits, the 740Le xDrive comes with everything you could possibly need to keep VIPs happy over long distances.
The LWB version tested here is more than 5.2m long and offers acres of space. Fitted to our test car is the Executive Lounge pack (costs an additional £6,675) that includes massaging, heating and ventilation functions for the super comfortable seats, a tablet-style centre console control system, and the front passenger seat moves forwards by 90mm to create even more space and resemble what it's like to fly business class.
BMW has the Mercedes-Benz S-class firmly in its sights with the latest 7-series, and on stylish kerb appeal and gravitas, the Merc still very much leads the way. For all its accolades, from the outside the 7-series looks too much like its 5-series sibling.
They're both exceptionally comfortable and spacious, the BMW boasts the bigger boot, and when both are in plug-in hybrid form, the 7-series offers the greater range and lower CO2 emissions too, although the S-class is more powerful and fractionally quicker.
It's a closely fought battle, but BMW has the cost advantage with a whole-life cost figure of 132.9p, significantly lower than the S-class's 157.3p. The 7-series also holds a 2% residual value advantage at 35.7%.
BMW 740Le xDrive Saloon
Model price range: £63,530-£80,330
Residual value: 35.8%
Service, maintenance and repair: £4,132
Vehicle Excise Duty: £0
National insurance: £4,406
Cost per mile: 132.9p
Fuel consumption: 117.7mpg
CO2 (BIK band): 56g/km (11%)
BIK 20/40% per month: £146/£293
Warranty: 3yrs/unlimited miles
Boot space: 420 litres
Engine size/power: 1988cc/258hp petrol engine + 112hp electric motor
From the outside the 7-series may look a little ordinary, but slip behind the wheel and it's a different story. The sheer volume and excellence of kit on offer is simply astounding. The addition of the plug-in hybrid system makes this car even more appealing thanks to the tax benefits, and it's here where the 740Le xDrive beats its Mercedes rival hands down.