Wind installation and support ships have been burning diesel and counting it as green fuel. The justification is that the wind power they are installing more than makes up for all the carbon they emit.

But that is set to change as charterers, governments and financiers sharpen emission requirements. Owners in this Norwegian-centred industry are competing to be the greenest.

Shipowners are ahead of their wind farm customers in thinking about decarbonisation, say some, because wind farmers consider their project green by definition.