The first power has been generated from the world's largest offshore wind farm, the companies behind the scheme say.
The first phase of the London Array project, around 12 miles off the coasts of Kent and Essex in the Thames Estuary, will see 175 turbines generating enough power to supply more than 470,000 homes.
Already 151 turbines have been installed since construction began in March 2011, and when the first phase is completed by the end of the year, the 630 megawatt scheme will be the largest offshore wind farm in the world, the companies said.
If approved, the second phase will add enough turbines to bring the total capacity of the wind farm to 870 megawatts. The plans have had to be resubmitted with a reduction in the area the turbines would cover following concerns the scheme would hit the red-throated diver population in the estuary.
Dong Energy has a 50 per cent stake in the project, energy giant E.ON owns 30 per cent and Abu Dhabi renewables company Masdar has a 20 per cent stake.
Benj Sykes, wind UK country manager at Dong Energy, said: "With its 630MW the London Array project will be the first of the next generation of larger offshore wind farms and we are pleased to have reached first power.
"Being able to efficiently develop large offshore wind farms and harvest the scale advantages in both construction and operation is an important element in our continuous efforts to bring down the costs of energy of offshore wind."
Dr Tony Cocker, chief executive of E.ON UK, described the first generation of power as an important milestone not only for London Array but for the global renewables sector.
He said: "We firmly believe that electricity from renewable sources has a vital part to play in helping us deliver energy in a way that is sustainable, affordable and secure and this is why we are aiming to reduce the costs of offshore wind by 40 per cent by 2015."