BMW’s plug-in hybrid powertrains have proved instrumental in maintaining the brand’s fleet presence in the past few years, filling the gaps in its line-up as it brings more electric models to market.

The 5 Series plug-in hybrid has been particularly important. With no direct electric alternative in the segment, cars like the 530e have been a key driver of fleet registrations by providing performance, luxury and low tax bills.

BMW responded to the 530e’s popularity by expanding the choice of plug-in 5 Series models from one to four. Alongside the rear-wheel drive saloon, there’s the 530e Touring, an all-wheel drive 530e xDrive and the 545e.

The latter is the car we’re testing here. It uses the same gearbox-mounted electric motor, 12kWh battery and all-wheel drive system as the 530e xDrive, but this time mates it with a six-cylinder 3.0-litre petrol engine instead of a 2.0-litre four-cylinder unit.

It boosts power by almost 100PS, when compared with a 530e, while improving refinement and providing an enhanced visceral experience thanks to its enhanced exhaust note.

The larger engine has a modest impact on the car’s official efficiency, with the 545e returning up to 156mpg and 41g/km of CO2. It also promises the same 33 zero emission miles as the 530e xDrive.

In practice, the more potent plug-in does burn more fuel. During our testing, which included a few charge cycles, the car was achieving 42mpg. Our previous experience in the 530e suggests more than 50mpg can be achieved in similar usage.

We found the battery to be capable of powering the car for around 27 miles before fully depleting its charge, although the 545e works best if you use the Adaptive drive mode and let the car decide the best time to deploy electric or petrol power based on your route and driving style.

All 5 Series plug-in hybrid models sit in the 12% benefit-in-kind (BIK) tax band. In best-selling M Sport trim, the 545e has a list price of £64,970 and will cost drivers (40% taxpayer) around £259 per month in company car tax.

A 3.7kW on-board charger means the battery takes almost four hours to recharge, which puts the BMW on the back-foot when compared with rival Audi and Mercedes models, which can charge twice as quickly. It means drivers are less likely to make use of destination charging, unless they have a lengthy stop, but should have little impact on those that charge up overnight.

With 394PS and 600Nm, the 545e provides fierce acceleration – achieving a 0-62mph sprint in less than five seconds.

Alongside strong performance, it’s the silky-smooth demeanour of the six-cylinder engine that makes the 545e a stand-out model in the segment.

The 545e carries an £8,000 price premium over a 530e, but is only £4,000 more than the cheapest Mercedes E 300e and £6,000 more than an entry-level Audi A6 50 TFSIe. The Audi offers a more attractive 8% BIK, but both cars are more comparable to the 530e when it comes to performance and running costs.

Opting of the 545e is, therefore, a heart decision. It offers superior performance and refinement, but in a segment where the bar is already exceptionally high. In just a few years drivers have migrated from sub-200PS diesel models into these higher-powered petrol plug-in hybrids. The 530e, and its key rivals, already offer drivers everything they need in the executive saloon segment, but the 545e steps things up to a new level while retaining fleet credibility.