Is anybody old enough to remember the phrase ‘light-off’? That’s nothing to do with the clocks going back, but it became a much-used line in the car industry a couple of decades ago.

‘Fast light-off’ referred to the amount of time it took for a then-new catalytic convertor to warm up sufficiently to clean up the pollution emitted by an engine, particularly when the engine was still cold.

The problem was that catalysts had to be reverse-engineered into existing cars and that wasn’t always easy. The first cats were simply fitted into the exhaust system, because there was usually some wriggle room in a car’s centre tunnel to house what looked like a big silencer box.

That was not the ideal position for the cat, which needs to warm up quickly. The best place for it was up near the engine manifold. But such a major bit of re-engineering and packaging usually has to wait until a car maker can incorporate the changes when a new generation of engine arrives. And that’s something that can take years.

The introduction of the first serious pollution laws in the European Union in the early 1990s meant catalysts had to be fitted to all petrol cars. Because most mass-market cars also still used carburettors, it meant a wholesale switch to fuel injection.