THE demand for posher and more spacious luxury sports utility vehicles continues unabated and Lexus has now added to the mix with a genuine seven-seater version of the standard RX model which goes head-to-head with its arch rival, the Volvo XC90.

Called the RX 450hL and with an extra third row of seats in the back Lexus has achieved this with a little bit of subtlety by using the same wheelbase as the five-seat version but extending the length at the back by 100mm as a slightly longer overhang.

In addition there's a more upright rear windscreen to give a pair of adults sitting in seats six and seven more headroom while foot space has been enhanced by slightly raising the middle bench of seats.

Full marks to the Lexus backroom design team since adding the extra length to accommodate two more seats has not been done as an afterthought - the rear end looks stylish and overall is in keeping with the smart looks of the original RX which remains one of the best looking big SUVs around.

Getting in and out of any third row of seats in a big car has always been a bit of a bugbear but again subtlety is the key in this longer RX. All that is needed is to simply fold down the second row of seat backs down and slide the bench forward via one lever and there's plenty of room for access.

A bonus for the third row of passengers is that they have their own triple zone climate control - and there are two cup holders too.

With 495 litres of boot space available with seven seats occupied reverting it to a five-seater and creating 966 litres of luggage space is again a simple task when with the push of a button the third row of seat backs fold down flat.

These super posh SUVs are of course not cheap but this extended RX 450hL, which is being offered with a choice of three levels of trim, is certainly competitively priced compared to its rivals.

The entry-level seven-seater SE costs £50,995 - some £2,305 premium over the equivalent entry-level five-seater SE, while the mid range Luxury version, expected to be the best seller, comes in at £59,095. The range-topping Premier is £61,995.

In terms of power there's no change from the five-seater RX as this extended version is a self-charging full hybrid system using the same 3.6-litre direct injection V6 259bhp petrol engine along with two AC electric motors - one powering the front wheels and the other the rear wheels making it an all-wheel drive system providing a total of 308bhp.

There's also the same CVT transmission as is the Drive Mode Select system where the driver can choose between different settings - Eco, Normal and Sport. There's also all the safety features featured on the five-seater RX and it has the Euro five-star NCAP rating too.

From a driver's point of view in all honesty there's not too much difference in how this seven-seater drives and handles compared to the five-seater - most motorists won't notice a change - although putting it into sport mode does give a little extra punch in terms of acceleration.

This latest version, like all the other RX models, is about enjoying a comfortable, smooth performance that's quiet, corners well and with such an excellent CVT gearbox it's extremely relaxing to drive whether in and around busy city streets or out on the open motorway.

Fuel consumption is rated officially at 47.9mpg which eqautes to a CO2 emission figure of 136g/km while on the performance front it can manage 0 to 60mph in eight seconds with a top speed of 112mph.

Even on the launch driving around the narrow, twisty mountain roads of Switzerland it remained stable, competent without any dramas helped too by its excellent adaptive suspension and general sure-footedness.

This Lexus hybrid system is still currently the best on the market in my book because it's highly efficient, smooth and quiet making the car so relaxing to drive and be a passenger.

It really doesn't matter which of the three trim/equipment levels chosen it's executive style all the way with the cabin layout and good, fully lumbar supporting seats and the overall interior finish is top class while for the driver all the control and instruments are simply sensibly laid out and so easy to use.

The entry-level SE grade is a good package with its 18-inch seven-spoke alloy wheels, full navigation system, leather upholstery, heated and ventilated front seats, power tailgate, LED lights and much more.

Obviously moving up to the slightly more expensive Luxury and finally Premier kitted models which both sit on 20-inch wheels there's even more quality furnishings and fittings and again the interior just oozes quality from end to end.

At the end of the day though as to whether a buyer goes for the five or seven-seater then naturally it's down to individual needs and tastes - for example that extra £2,305 for the SE with those extra seats is well worth it if a large family has the need for a top premium SUV with extra space.

As usual it's horses for courses but one thing is certain - this latest batch of RX SUVs won't disappoint.