I test sailed the Lagoon 420 yesterday (Thursday 7 June). Now the USP of this boat is its hybrid engine system; two electric motors drive the yacht powered by two banks of six batteries connected in parallel to deliver 72 volts. These are charged by an 11KVA diesel gen-set which also supplies 12V DC and 220V AC current. This means the Lagoon can be stacked with dish washers, washing machines, air conditioning, microwave ovens, computers, you name it.

The whole system is controlled by electronics that balance battery voltage and capacity against consumption, automatically start the gen-set when required, and, when under sail, use the spinning props to augment the charge from the generator. The electronics on this boat are hugely complex and sophisticated and it has taken Lagoon a long time to get it all to work – indeed, our trials had been postponed on a number of occasions because of trouble in this department.

So when I finally got on board I was at least half expecting some sort of breakdown in the day ahead. And what was it that brought this expensive, sophisticated, interlocking system to its knees?

A burnt-out impellor on the generator cooling system.