To celebrate its 50th anniversary, Caterham has unveiled the most powerful Seven ever; the X330 - a one-off supercharged model boasting a mind-boggling power-to-weight ratio of 600bhp per tonne.

The stealthy, matt black concept is based around the range-topping CSR Superlight, but the addition of a supercharger to the four-cylinder 2.3 litre Ford Duratec engine increases power massively from 260 to 330bhp - as the name suggests.

That means the X330's equivalent power-to-weight ratio puts it ahead of the Bugatti Veyron (521bhp per tonne) and the McLaren F1 (559bhp).

The near 35% power hike is achieved by a Rotrex C30-94 supercharger, which provides a boost characteristic that rises linearly with engine speed. In other words, although the X330’s punch is greater at higher revs and speed, low-speed driveability isn't compromised thanks to an exceptional torque curve with over 221 lb-ft from 5500 to 7500rpm - 20 lb-ft more than the CSR260.

As the X330 is an engineering test bed it is envisaged that some of the concepts will eventually find their way into production. To begin with the X330 will spearhead the British firm's R&D into bioethanol power in the coming months as it seeks to assess the viability of alternative fuel sources in road and race applications and cement a further 50 years of history for the legendary Seven.

In keeping with the Seven ethos of "adding lightness", the extremity of the X330 doesn’t stop at moving parts. Lighter gauge steel is used in the trellis-style chassis and the use of new lightweight wheels together with an abundant use of carbon fibre for the bodywork all adds to the stealth appearance of this perfect 50th birthday present.