Ford’s EcoBoost engines have a bit of a track record with blown head gaskets thanks to the fundamental design of the crankcase where it meets the cylinder head. Given the relatively high turbo-boost pressure some of these engines use to produce their impressive performance, the head gasket can fail.

But it’s also fair to say that this engine design has also seen its share of overheating problems, blown turbochargers and coolant leaks (often into the cylinders). With that in mind, don’t bother guessing what the problem is, allow a mechanic to inspect the engine and give you a professional opinion based on facts.

It doesn’t take much of a leak to allow enough rainwater into a car to wet the carpets. Given your car is a 2018 model, I’d be surprised if the rubber seals have deteriorated to any great extent. The best bet is to open the doors and hatch and have a close look at the surface of the seals. If there’s a nick or a cut in the rubber, you’ve probably found the problem. But also look for a twig or other piece of rubbish that could be stuck to the rubber and be forming a gap for the water to enter.

If the front floors were wet, the advice would also be to check the drain hose for the air-conditioner, but if it’s the rear floors, it’s almost certainly rainwater. Don’t forget the obvious stuff like a window that looks closed but is actually open a fraction.

There are lots of potential causes for this sort of behaviour, starting with an alternator that is not working properly or even a body computer that is on the way out. But these symptoms are also a classic indication of a very simple problem; a poor earth somewhere on the car. A modern car has multiple earthing points, and if one is a bit sketchy, it can throw the whole car into chaos. Flickering lights and gauges and warning lights on the dashboard are classic indicators of a bad earth. If that’s the case here, an auto electrician should be able to chase down the fault and fix it permanently.