Over the past seven days, Nissan has welcomed media from all over Europe to sit inside its prototype Leaf and see for themselves how it fares on a pre-set route around east London. I was there to ride shotgun with Tetsuya Iijima, General Manager of Autonomous Drive Development at Nissan, through the streets of Beckton, onto the A13 dual carriageway and back to the ExCel, a short distance from London City Airport and across the river from The O2.

Why?

It's not the first time the company has conducted a trial with the car -- they've tested it in Japan and Silicon Valley before -- but European roads pose a unique challenge thanks to an abundance of pedestrian (zebra) crossings, roundabouts and the unpredictable nature of London's drivers. Before fully autonomous Leafs can be sold in glitzy showrooms, Nissan needs to prove it can master each of these obstacles without error.

From a distance, the autonomous Leaf looks like any other Leaf you'd see on London's roads. Up close, however, it's a different matter. Dotted around the car are four lasers, five radars and 12 cameras, most of which have been seamlessly integrated into the bodywork, that provide the car with 20 centimetre accuracy. The two enclosures located on top of the car, which almost look like ears, are obvious but it took me almost an hour to recognise the sensor built into the Nissan badge just underneath the bonnet.

In the boot -- the entire boot -- lies the processing power. Stacks of computers connected with numerous cables collect and analyse the data generated by the car's sensors. It shows that while much of the technology is available to car makers now, minimising its footprint and integrating it into a production vehicle will take some work.

In the front are three displays. One offers a typical satellite navigation interface and another feeds back footage from the front camera. The final screen shows where the car is in comparison to the environment around it, highlighting pedestrians, vehicles and obstacles as it encounters them. Before we set off, Iijima-san explained that the displays are meant to help passengers; they're not necessary for the Leaf to perform its duties.

On the road

Although the UK is moving swiftly to introduce new laws governing the use of self-driving cars, Nissan's tests must adhere to broader legislation. It means that while Iijima-san doesn't need to touch the steering wheel or the pedals during our 25-minute journey, he must sit in the driver seat and be ready to take back control should the car fail to operate as it should. Nissan notified Transport for London (TfL) and the Metropolitan Police of its plans before the tests and fitted independent front- and rear-facing cameras to capture footage (to present alongside its own data) in the unlikely event of an accident.

"The technology is separate in two parts: common and regional. For the UK, zig-zag lines and lighted crossings need to be understood before we can bring a car to the market," said Iijima-san as we first entered the car. "We need to expand the area of the testing before we meet the regulations and rules of the area. That's why we're here today."

When the time came to depart the hotel car park, the Leaf's autonomous mode was enabled and Iijima-san removed his hands and feet from the controls in an eccentric manner, perhaps playing up to the fact we were paying little attention to the road. Then, to underline the UK's love affair with roundabouts, Nissan decided that the first part of my journey must incorporate no fewer than six of them.