So if you consider the Prius purely for its rational benefits – reliability, practicality and fuel efficiency, boosted further by the environmental credibility of not churning out diesel fumes – then there’ll be no real surprises from this seven-seat version. It’s a Prius and a bit – larger load space, extra headroom and a couple more seats which fold up out of the boot floor, and a little slower as a result.

The MPV sector is ruled by the diesel engine – torque and fuel efficiency are vital for hauling a large family around. So the Prius+ is a unique proposition with its hybrid drive, taking the MPV sector down to double-digit CO2 emissions in its most popular T4 trim level – expected to account for 80% of UK sales.

With low tax, high efficiency and congestion charge exemption (at least for the near future) this is predicted to be an attractive fleet car. But to work, it needs to pull off the capacious talents of an MPV with the tech-rich eco appeal of a Prius hatchback.

Globally, scaled up Prius comes in two forms which are essentially the same car. Prius V, sold in America and alongside the Prius+ in Japan, is the same vehicle but with a nickel metal hydride battery under the boot floor. Prius+ tucks a lighter, but more than twice as expensive, lithium ion battery into the centre console between the front seats giving space for a third row in the boot.

Some of the packaging differences are evident. The Prius+ has a cubby hole suitable only for a DVD case between the front seats and the boot floor is level with the top of the bumper. There’s a small compartment underneath to hide valuables in – presumably a redundant space where Prius V has its battery.

The gains in boot space from shifting the battery up front are what allowed Toyota to get the mechanism for the third row mounted as low as possible, and Prius+ was considered to be a gap-filler for the European market. It leaves stacks of cabin space, too, with plentiful of head and leg room in the centre row and individually-adjustable seats to offer more space for baby seats and broad shoulders.

But the third row is really for children only. The raked roofline offers minimal headroom, and the middle row doesn’t return to its previous position after tipping forward to access. There’s enough room to have the middle row slid forward and have space for adults in both rear rows, but the sloping footwells in the back don’t offer a particularly comfortable seating position for adult occupants.

It’s a flexible setup, though. All except the driver’s seat can be folded flat with a simple button, and although none are removable this does create a sizeable, level load area. With loads of legroom in the middle row you could almost view this as a more luxurious Prius with estate-like load capacity and the useful option of some emergency-use seating when needed.

Toyota is being conservative with its sales estimates for the Prius+, at just over 2,000 units in its first full year, offering tax-conscious, eco-friendly motoring for larger families. But, rather like the first Prius, it’s really a step towards what should become a more refined, capable product in the next generations.

Verdict:

Prius+ is entirely a head over heart purchase, but it’s really a car that’ll enjoy its biggest demand among Prius hatchback owners wanting to upscale without defecting to a non-hybrid powertrain. Clever packaging, respectable practicality and low running costs will please the early adopters.

Specification:

Segment: MPV

Type: Petrol-electric hybrid

Price: £26,195-£29,495

Electric range: 1.2 miles

Fuel: 64.2-68.9mpg

CO2 emissions (tailpipe): 96-101g/km

Charging port: N/A