I've just spent a couple of days at the Monteblanco circuit near Seville, surrounded by Mercedes-Benz concept cars and engineering demos. This 'TecDay' event was amazing - in more ways than one.

The cars and the technology were incredible. Witness F700 (pictured above), the latest in a line of Mercedes research cars, which has a clean, efficient DiesOtto engine and Pre-Scan suspension which reads the road ahead to actively prepare the car for bumps. You can read more about it in my review for CAR Online.

What really amazed me, though, was the time and trouble Mercedes had taken to give us hacks access to its advanced engineering. Concept cars were only one part of it: we also had senior engineers on hand to grill for information, demos and displays to explain how everything worked, and a mountain of printed information to put it all into context.

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Mercedes is clearly very keen to show just how much effort it is putting into developing new technologies for tomorrow's cars.

But ask how the compression ratio is varied on the DiesOtto engine, or when the engine will appear in a production car, and at best you get a non-committal answer.

TecDay might feel like an Access-All-Areas event, but Mercedes still has a few secrets it wants to keep.