We are back at Millbrook Proving Ground, and at last we have a chance to try the Smart Electric Drive – alas a very brief chance, and on the low-speed “city” circuit of tight twists and turns, not on Millbrook’s famous high-speed bowl or hill circuit.

It’s a dazzling day and the glassy Smart is cultivating a greenhouse effect of its own inside. There’s no aircon to tame the September heat.

Next year’s second-generation Smart ED will feature a Tesla-developed battery pack, but our car is the first-generation model. It is based on the facelifted original ForTwo (or City Coupe as it used to be called) fitted with an electric drive system by British firm Zytek. This uses sodium-nickel chloride batteries bolted under the seats, and a 55kW (74bhp) motor replacing the usual three-pot petrol engine at the rear.

From the driver’s seat the car is virtually unchanged from standard. There’s even a (non functional) fuel gauge among the instruments.

One of the Shrek-ear pods that sprouts from the dashboard now displays remaining battery capacity. Unusually for an electric vehicle, this is an analogue clock – its plastic hand pointing to about 80% as we clapped eyes on it. There is no attempt to translate this reserve capacity into useful range – that’s left as an exercise for the driver.

Smart quotes 72 miles between charges, and eight hours for a full charge.

The ignition key slots into the centre console next to the handbrake. Ahead is the stubby, joystick-like transmission lever. This has a gate shaped like an inverted “L” – to the left for drive, to the right for neutral, and back for reverse. It has a nice, mechanical feel to it.

Once switched on and ready to go, the motionless ED is not silent – there’s a quiet but noticeable thrumming noise coming from the power pack behind you, and a faint vibration you can feel through the brake pedal.

There’s a slight hesitation between pressing the accelerator and the Smart deciding to get up and go from a standstill. In an ordinary Smart, this could be blamed on the oft-criticised automatic transmission, but that can’t be the culprit here, as the ED has only one constantly-engaged ratio. The delay is not enough of a cough to get you T-boned at a junction, but just enough to make you think you might. Throttle response once on the move is instant, though.

At low speed, the unassisted steering felt reasonable light and direct, and speed was easy to modulate accurately.

There is a distinct squeak from the drivetrain as you set off, and more whine from the motor than we’ve heard in other electric cars. This singing from the Smart’s oily bits rises in concert with road speed, and here the ED is impressive. It is a quicker car than you actually need for city driving, between zero and 40mph at least.

Smart quotes a 0-30mph time of 6.5 seconds, which feels about right, while Zytek says the motor should be good for about 75mph. Smart has electronically capped progress at 60mph. It feels safe, solid and serene at speed, with no rattles or squeaks.

On our bone-dry test surface we failed to provoke understeer, and the firm suspension kept roundabout lean angles to a minimum. We suspect the central, low-slung battery gives a better weight distribution to the normally rear-biased ForTwo, together with a helpfully lower centre of gravity. Around corners and roundabouts, the car felt secure and very safe.

As long as you never turn left, that is. The combination of a relatively low header rail and a high seat base meant the rear-view mirror created a monster blind spot for us just where the road needed to be on sweeping left-handers. If the car were ours, we’d be seriously tempted to wrench the rear-view off entirely and rely on the door mirrors alone.

All in all, we liked the Smart ED more than we thought we might. It’s not perfect by any means – the tiny boot, poor driving position and low-speed hesitancy are distinctly black marks. But it feels solid and well-engineered and would probably keep you alive in a crash.

Would we buy one? Cost will be the issue – and for the production ED that remains to be seen.