So Porsche has finally done what it always said it would not do and is going to put a diesel engine into one of its production cars. 

But for those of you who think a diesel is about as appropriate a power source for a Porsche as a steam engine for an F1 car, it requires nothing like the mental leap we all had to make when Porsche abandoned half a century of building lightweight two door sportscars and produced a two tonne, five door, cod off-road leviathan called the Cayenne.

And history recalls the buying public in general and the Americans in particular took to the Cayenne in their hundreds of thousands. Truth is the Cayenne owes nothing at all to traditional Porsche values and if putting a diesel in one will make it more frugal, give it a better range while still performing approximately as well as the already hardly electrifying standard Cayenne, then who cares?

Not me. It's when they conclude its a good motive source for a Cayman or a 911 - otherwise known as proper Porsches with proper Porsche values - that we should start to be really concerned.

Personally I think the last well will run dry before Porsche lets that come to pass.