In December, the Department of Trade and Industry and Environment Department (DEFRA) announced they would give the wind farms the relevant consents under the Electricity Act 1989 and Food and Environment Protection Act 1985.
London Array, being developed by a consortium that includes E.On UK and Shell WindEnergy, will consist of over 300 turbines and be capable of generating 1GW electricity.
It will be built 12 miles off the Kent coast in the Thames Estuary.
It will now include only 175 turbines - down from 258 - to ensure it does not affect populations of red-throated diver.
A date for the start of construction will not be set until the outcome of a public inquiry into a proposed substation at Cleve Hill, Kent.
In contrast, the Thanet wind farm is being "fast-tracked" by its developer Warwick Energy to be operational in 2008.
The 300MW project, consisting of 100 3MW turbines, will be located seven miles off the east Kent coast.