These days it's not often a car is still in production to see its 10th birthday; not without some serious reworking anyway. It's rather astonishing, then, that the Caterham Seven will very soon be 50!

While the Seven itself shows no signs of hanging up its keys just yet, it won't be celebrating the milestone with its trusty powerplant. The Rover K-series engine is replaced with a younger model next month in the form of 1.6-litre Ford unit. Chosen due of its lightweight construction, low emissions and unusually flat torque curve, the 'Sigma' engine is also more powerful, which is never a bad thing.

Aesthetically unchanged, the 2007 Caterham also benefits from a 12 percent increase in torsional rigidity thanks to a new precision laser-cut, robot-welded manufacturing process. The added stiffness is said to have improved cornering performance and handling feel. To ensure that the changes are worthwhile, Caterham completed more than 10,000 road, and 1,200 track miles during development of the new model; the most rigorous R&D programme in the company's history.

At launch, customers will have the choice of two power outputs (125bhp and 140bhp), although an even more powerful version will also be available next spring. The 140bhp variant will also be available from launch in stripped-out Superlight form giving a massive power-to-weight ratio of 280bhp per tonne. Prices listed below for the new models are virtually unchanged, although remember to add £2,500 if you don't plan on building the thing yourself...

Caterham Seven Roadsport 125
Maximum power......125bhp at 6100rpm
Maximum torque......120lb.ft at 5350rpm
Weight.....................550kg
0-60mph...................5.9 seconds
Power-to-weight......227bhp-per-tonne

Caterham Seven Roadsport 140
Maximum power......140bhp at 6100rpm
Maximum torque......to be confirmed)
Weight.....................550kg
0-60mph...................5.0 seconds
Power-to-weight......245bhp-per-tonne

Caterham Seven Superlight 140
Maximum power......140bhp at 6100rpm
Maximum torque......to be confirmed)
Weight.....................500kg
0-60mph...................4.7 seconds
Power-to-weight......280bhp-per-tonne