I set off yesterday on a 120-mile M4 journey in the Range Rover, with about 50 miles of fuel left in the tank. The sat-nav, as is its habit, soon sent me a message that I didn’t have enough fuel to complete the journey, and offered to redirect me to the nearest filling station. 

My reflex was to bat this offer away, knowing I’d find a filling station in the next few miles. But at the same time it occurred to me this was the very situation to that faced by drivers of current electric cars: the trip stretches ahead but they lack the range. But why, exactly, was I completely confident about facing the Range Rover journey when I know I’d have found it much more of a challenge in a Nissan Leaf or Renault Zoe?

The answers are obvious, you may think. Electric cars have shorter ranges. On a 120-mile trip you’d need to stop at least once for a 20-30-minute fast charge, and that’s if you start with the battery 'full'. But I’ve already investigated the fast-charging arrangements on London’s westerly motorway, and found it a straightforward, rather pleasant procedure. Not perfect if you’re in a hurry, but no disaster.

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So what was the nub of the problem? I kept thinking back to an early return trip to Oxford in a Nissan Leaf – at the end of which we very nearly ran out of charge. I can’t remember the exact words, but the machine started declaiming loudly that unless we stopped and pulled over, it would simply become immobile in the street.

Which was, I decided, the root of the problem. It’s acceptable to have a machine with a short range provided you have a means of getting it going when it conks, as you do with a petrol car with a gallon of fuel in your boot. Or in the hands of the RAC man. But no cranking or push starting will currently revive your electric car. It becomes a monument at the roadside.

Not any more, however. This week I heard about a new portable charging station called an EV Rescue. In effect it’s a big, smart battery that rolls on wheels like an airport suitcase and is made by a firm recently bought by Chargemaster, the UK’s biggest maker of EV charging stations.