There is nothing out here to highlight the scale of these machines. A blue-grey sky hangs behind the enormous structures; the boat we are on, 4 miles (7km) offshore from Liverpool, bobs excitedly up and down on the swell of the sea. We’ve come to the Burbo Bank Extension wind farm to see an engineering marvel: the largest wind turbines in the world.

When one of the turbine’s blades swings to its highest point, it reaches 195m (640ft) – making these structures nearly twice as tall as Big Ben. The diameter of the turbines’ three colossal blades is greater than that of the London Eye. As the huge wings sail by, cutting the air, they make a gentle swooshing sound.

The very first offshore wind farm was a Danish project. But Britain now leads the world. The largest offshore wind farm on Earth is the UK’s London Array, a massive site of 175 turbines in the outer Thames estuary. Up to 5.2GW of electricity are provided by the country’s offshore turbines – almost as much as the rest of Europe’s sea-based wind farms put together, with more than two-thirds of continental Europe's capacity. Beyond Europe, the rest of the world’s offshore wind totals just a few gigawatts.

Industry insiders say the significance of tapping the power provided by coastal winds ever more cheaply should not be underestimated. In December 2016, the World Economic Forum reported that as the cost of producing wind turbines has fallen by more than 30% in the last three years, the cost of electricity from wind power has fallen to $50 per megawatt hour on average worldwide, without subsidies. That’s half the cost of coal.