Monster wind turbines with blade spans that dwarf the London Eye could be the shape of future green power, it was revealed.

An offshore turbine more than 500ft tall with a diameter of 475ft is already due to make an appearance in British waters within the next two years.

But the 10 megawatt machine, dubbed Britannia, may only mark the start of a growing trend, according to the project's leader Bill Grainger.

He sees no reason why offshore turbines should not get even larger, since greater size and power make economic sense.

Mr Grainger, who heads the Britannia design team, told The Engineer magazine: "There isn't a technical issue that screams out size limit.

"You have to make changes as you get bigger. Blades get floppier, for example, so you have to put more carbon in, but we aren't anywhere near 100 per cent carbon yet."

Mr Grainger is engineering manager at Clipper Windpower Marine, the UK arm of the US company developing the 10 megawatt turbine.