BMW has released details of its new 7 Series luxury saloon, a firm favourite with chauffeurs and high-end executives.

This update of the flagship four-door brings few major changes, but the many refinements throughout its design are designed to make it more comfortable, more economical and more luxurious.

Externally the car is 8mm lower than before and wears the latest version of BMW's `kidney' grille. Small chrome details on the front and rear bumpers and a deeper shade of red for the rear light clusters accentuate how small the exterior changes are.

Inside the cabin looks much the same as well, but extra soundproofing has been added around the B and C pillars, the sills and the boot area. Variable-colour ambient lighting is also new and there are myriad options for audio, communications and materials.

Most of the key technological and luxury highlights are optional, allowing each 7 Series to be effectively customised to the needs of each specific buyer.

A range of petrol, diesel and hybrid drivetrains are available across two wheelbases. The `L' long-wheelbase 7 gives rear passengers 140mm more legroom and 10mm more headroom for an altogether more spacious feeling.

The entry-level 730d will be popular in Britain, now featuring a 254bhp six-cylinder diesel and costing £58,115. There is also a 740d with a stunning 309bhp version of the same engine for a £7,190 premium. CO2 emissions are sub-150g/km for all the diesels.

On the petrol side the range starts with the 316bhp six-cylinder 740i, an engine that's also used in the `ActiveHybrid7', otherwise known as the 7 Series hybrid. A 55bhp electric motor is added to the drivetrain and allows electric-only running for short spells and reduces CO2 to 158g/km. It starts at £11,025 more than the 730d.

There are also £71,340 750i and £101,805 760i variants. The former's 4.4-litre V8 produces 443bhp and 199g/km of CO2, while the thumping six-litre V12 in the 760i pushes out 537bhp and 314g/km.

The new 7 Series will go on sale towards the end of September this year, with SE and M Sport trims available from launch.