Two days, two range-extenders. Last Friday, I travelled to Ballymena in Northern Ireland to see the first production example of the new London bus (powered by a 4.5-litre diesel engine/generator and 17kWh battery) and then immediately hot-footed it (via taxi, plane, Nissan Leaf, feet, train and feet) to Brighton to drive the Chevrolet Volt (1.4-litre petrol engine/generator and 16kWh battery) in the Future Car Challenge.

It’s a year since I drove the first Chevy Volt at the launch in Michigan and my view of the car hasn’t changed. It still looks and feels like the future, even if this first-generation powertrain is not without its conceptual flaws.

The Brighton to London run in the Volt was a game of two halves: the 65.8 mile drive was conducted almost exactly 50:50 between the battery and the petrol-powered engine/generator.

The battery pack was actually charged up last Monday, before the Volt left GM’s care in Germany, so when we fired it up before 06:00 on Saturday morning there was a suspicion it wasn’t operating from the full 100 per cent.

Even so, we got 35 gently-driven miles out of it (including getting to the start line) before the battery charged dropped to around one-third (the Volt never fully de-charges its battery) and the engine/generator started to kick in.

The engine/generator used 0.85 gallons to cover 33.6miles (of which about half was busy urban driving), so the actual fuel consumption was 39.5mpg. In the weird world of the EU economy cycle, the battery power is Co2-free, so our ‘official’ economy was 78.4mpg.

And we were one of the first cars to arrive in central London, because we didn’t exactly indulge in extreme eco-driving techniques.

Clearly, although it works amazingly well, there’s room for plenty of future development with range-extenders. The engine in this Volt is pretty much a standard-issue supermini engine/generator . The next-generation motor will be smaller and engineered to work better as a generator.

Moreover, from an economy point of view, this engineering solution is not ideal for the UK sport of hoofing up and down motorways at 80mph. Perhaps, one day, the ultimate solution will be a version of the Volt with an engine that can fully drive the wheels at motorway speeds (today’s Volt engine/generator does assist the from wheels at very high speeds) and, at town speeds, decouple itself and work as a generator.

Meanwhile, Autocar is looking forward to spending a bit more time behind the wheel of the first right-hand drive Volts.