BBC News online recently featured an interview with Justin King, chief executive of Sainsbury’s, which, intriguingly, did not focus on his hopes for the supermarket’s like-for-like sales or elaborate on plans to unlock greater shareholder value from the store’s property estate, but concentrated entirely on his new car, the apparently environmentally friendly petrol-electric hybrid Lexus LS600hl.

“The Lexus does 30 miles per gallon, which is fantastic,” he was quoted trilling as he was driven around in the £88,000 limousine that has replaced his £77,110 Maserati Quattroporte. “[However] the area between the seats and the boot is taken up by batteries, so there are performance sacrifices.”

I was impressed. So much so - the idea of pandas drowning in ice cap water upsets me as much as the next man – that I called Lexus to ask for a test drive, to experience for myself the car’s eco-enhancing qualities. It arrived two Thursdays ago and the first day was a remarkable success: the Lexus was left in a neighbour’s parking bay and towed away as a result, meaning I didn’t drive it and hence contributed zero carbon into the atmosphere. Hooray!

But the remainder of the loan witnessed patchier results. Friday: unplanned drive from home to work car park, and subsequent unplanned Tube journey home, because the 5.15m Lexus didn’t fit in my home parking bay (CO2 increase of 5.1kg). Weekend: journey from London to Wolverhampton and back again that would otherwise have been done by train: (83kg increase in CO2 ). Monday: entirely unnecessary trip to country because I’d developed an attachment to the car’s 19-speaker Mark Levinson Reference Surround System (17kg of CO2 ).

You get my point. The Lexus may be less polluting than a 14.9mpg Maserati or, say, the 1989 Exxon Valdez oil spill, but it is still polluting. It will do for the pandas, and perhaps the polar bears, too, what John Prescott has regularly done for Mr Chu’s menu in Hull. But, having said that, my four days in the closest thing you can get to a private jet on the road didn’t make me think Justin King was mistaken for broadcasting his ownership.

But before I explain why, I need to highlight one particular thing about British business’s conversion to the environmental cause: it has been sudden. So sudden, in fact, that I missed it, as I was at the time on sabbatical. Having taken a break of around nine months from business journalism in 2006-07, I was expecting to return to a corporate world that was, as ever, oblivious to the planet’s accelerating ecological collapse, but instead found companies suddenly competing to promote their environmental credentials.

Someone had even coined a new phrase – “greenwash” – to explain how corporations were disseminating disinformation so as to present a responsible public image. But even this phrase didn’t convey the extent of the revolution. Many companies weren’t just trying to make out they were green, they were trying to make out they were Greenpeace. And some of these companies, such as BP, claiming to go “beyond petroleum”, had caused the worst environmental destruction.

The last time that I had felt so surreally out of touch was when I had spent a summer in the United States and returned to find people exclaiming “zig-a-zig-ahhh” in the middle of conversation: the Spice Girls had landed.

And here we have the first reason King should not be mocked for his Lexus: it is a tiny gesture, but compared with other examples of corporate environmental hypocrisy, it is insignificant. Even within the context of executive cars, there has been worse behaviour: Sir Stuart Rose at Marks & Spencer made a big deal of switching his Bentley for a hydrogen-powered BMW last year, but it has subsequently transpired that he has swapped it for a petrol BMW, has a Bentley for personal use and uses private aircraft to travel around the country.

Another reason not to mock King: it’s not easy, as Kermit the Frog once complained, being green. The advice on what is environmentally beneficial keeps changing. Two years ago, biofuels were touted as the solution to our imminent global demise, but now it is said that they threaten food supplies, rainforest and climate. A similar thing has happened with carbon offsetting, with many people now questioning the benefits of certain types of offsets, and with “green” cars, too.

Toyota’s Prius may have become a byword for eco-friendliness, but a recent report claimed that if you take into account the energy used in producing and disposing of vehicles, the petrol-swilling Jeep Wrangler is actually greener. Meanwhile, other experts like pointing out that many diesel cars exhibit better fuel economy than such hybrids and that even electric cars aren’t truly emissions-free, given that CO2 is produced at power stations. Within this context, King’s argument doesn’t seem so silly.

But the third and main reason why King shouldn’t be ridiculed for his new toy is that he runs a corporation, and corporations are, because of their size, incapable of doing anything with any subtlety. Changing corporate culture takes time and British business is still at the stage with the environment that it was with race in the mid-1980s, when “diversity” comprised little more than a chief executive posing with a single black employee, usually a cleaner, on the cover of the annual report.

Business’s attitude to race has since become more sophisticated, and it will do so in relation to the environment, too. The Lexus may, like many corporate green gestures, be a gimmick and its size may mean it emits many times more the CO2 of smaller cars, and, yes, of course, if King really wanted to make a difference, he would travel by public transport, but at least it is a start, a sign that Sainbury’s has begun to think about the environment. And the planet needs every gesture it can get.

sathnam@thetimes.co.uk