Just a quick note to thank you for your advice. Having always burst into life at the first turn of the key, our 105,000-mile Renault Clio developed an intermittent starting problem. When this occurred, the engine turned over fine, but showed no signs of firing. You told us that a common problem with Renaults of this age was failure of the flywheel position sensor or its cable or the connectors. We changed the crank position sensor (which came with a mini loom attached eliminating one connector), and the car has been faultless since.