A couple of years ago, Volvo made the headline-grabbing announcement that every model in its range would feature an electric motor somewhere in its drivetrain.

To some extent, it was already a good way towards achieving that goal with the T8 Twin Engine plug-in hybrid (available on XC90, XC60, S90, V90, S60 and V60).

That’s since been joined by the T5 Twin Engine option for the XC40, as well as Volvo’s first fully electric vehicle in the guise of the recently-revealed XC40 Recharge.

But that still leaves a few gaps in the line-up, particularly on larger models such as the XC90 that have traditionally relied on diesel power.

Perhaps not surprisingly, then, Volvo has come up with an answer: the XC90 B5 mild-hybrid.

It combines the familiar 2.0-litre four-cylinder 235hp turbodiesel with a modest 10kW, 40Nm electric motor powered by a small 48-volt battery.

The battery is recharged during braking and deceleration, with the power used to drive the car’s electrical systems or provide assistance during acceleration via the electric motor.

With the 48V battery powering the car’s systems, the length of time the start/stop system can keep the engine off is extended, saving fuel in heavy traffic, while the electric motor acts as a rapid starter, restarting the engine quickly and quietly when pulling away again.

That rapid restart is perhaps the only clue to the system’s presence – there’s no dashboard display to indicate battery level, for instance – although we did notice a couple of foibles with it.

The system attempts to maximise fuel savings by switching off the engine as early as possible, often before the car has come to a complete stop.  However, if the traffic begins to pull away while the car is still rolling, the engine restarts and engages drive very abruptly, leading to an uncomfortable jolt.

It can also be difficult to come to a smooth stop by gradually reducing brake pedal pressure; there’s a point in the pedal’s travel at which the engine restarts, and for my money that point arrives far too quickly, shunting you rather inconsiderately towards the car in front.

And in one final minor detail, we noticed that the instant mpg display would constantly flick between 6.4 and 99.9 mpg when coasting, suggesting that there are perhaps still a few software kinks to iron out.

Volvo claims the mild-hybrid system is capable of achieving a 15% improvement in fuel economy over the diesel-only D5 model it replaces, quoting WLTP-certified combined figures of 37.7-44.1 mpg.

On a 500-mile round trip – a journey the XC90 B5 managed easily on a single tank – we recorded an average of 41.6mpg, and although around town that figure dropped fairly quickly to around 35mpg, both are very respectable figures for a large, seven-seat SUV.

Volvo will add the mild-hybrid system to its petrol line-up later in the year, although rather confusingly it seems this will also be badged B5, creating two different powertrains fed by different fuels but with the same name.

Away from the engine bay, Volvo has made other changes to the XC90 for 2020.

There’s a new brake-by-wire system with a curiously rock-hard brake pedal, plus an updated eight-speed automatic transmission that seems to shift up through the gears with greater urgency than before.

The gears seem lower, too, and that leads to a more gradual and refined pull-away that will probably please chauffeurs everywhere, while downshifting during braking feels noticeably smoother than the previous transmission.

By happy coincidence, this new gearbox also makes the XC90 slightly faster, with Volvo now quoting a 0-62mph time of just 7.6 seconds.

That’s more than enough to scare off a few hot-hatches.  And remember, the B5 is the slowest XC90 in the range – the T8 Twin Engine gains a slightly larger battery for 2020 for a 28-mile electric-only range, and that completes the same sprint in just 5.8 seconds.

Also new for 2020 are a few modest styling tweaks: there are new grilles, lower bumper designs, and alloy wheels, while all models feature integrated roof-rails and dual exhausts as standard.  R-Design models gain gloss black exterior trim and a new Slate upholstery choice, there’s a new chrome tailgate strip for Inscription variants, and a trio of new paint colours.

We’ve long been complaining at the stinginess of being charged £300 to add a reversing camera to a £50,000 car, so we’re pleased to see Volvo has seen sense and now includes one as standard, along with a power tailgate, keyless entry, electric driver and passenger seats, and a data SIM with 100GB of data allowance for 12 months.

Everything else is XC90 business as usual, so that means the most accommodating and comfortable cabin ever devised by mankind, the same clear digital instruments, and Volvo’s typically intuitive and appealingly-designed infotainment system, now with Android Auto as an option.

These timely updates to the 2020 XC90 only serve to reinforce the conclusion we arrived at when we first tested Volvo’s flagship nearly four years ago: there is no better car for a long journey than a 90-series Volvo.

Entry-level Price£53,635Price as tested£59,360
Engine1969cc 4-cyl twin-turbodieselTransmission8-speed auto
Power235hp + 14hpTorque480Nm + 40Nm
0-627.6 secsTop speed137 mph
Economy37.7-44.1 mpg (WLTP)CO2154 g/km
Dimensions4953 x 2008 x 1776 (LxWxH)Kerb Weight2103 kg