Trade and industry secretary Alistair Darling gave his seal of approval to the 26-turbine wind farm at Little Cheyne Court, Walland Marsh, Kent, in October last year.
Mr Merricks, a farmer, of Icklesham, Rye, East Sussex, manages the Romney Marsh Nature Reserve, including the Cheyne Court Site of Special Scientific Interest (SSSI), and was in 1999 awarded an MBE for his services to nature conservation.
His counsel, David Forsdick, told London's High Court the scheme, backed by Npower Renewables Ltd, had been 'hugely controversial' from the outset and the case had 'general significance' to wind farm proposals all over the country.
The proposals had raised 'a number of hackles in the conservation world' and the barrister said that both English Nature and the Royal Society for the Protection of Birds (RSPB) had expressed deep concerns over the development.
And, although those bodies may have received 'some comfort' regarding how future wind farm proposals would be dealt with after 'very high level' negotiations with the DTI, he said any concessions made would assist Mr Merricks and local birdlife 'not a jot'.
Mr Forsdick argued that, in granting permission for the scheme, Mr Darling had applied standard planning criteria, rather than the 'rigorous precautionary approach' required by the European Union Habitats Directive.
The barrister said that permission could only validly be granted for the wind farm if an 'appropriate assessment' showed that the proposal would not 'adversely effect the integrity' of any Special Protection Area for wildlife.
And he argued that the numbers of birds - in particular Bewick Swans - overflying the site had been seriously underestimated.
That, he told the court, was because there was an 'abnormally intensive' level of crop protection 'bird scaring' going on at the time of the survey and the numbers of birds overflying the site at night had been inadequately assessed.
He said the long-lived and slow-breeding Bewick Swan population already suffered fatalities due to power cables in the area and even a small number of fatal 'bird strikes' by the generator blades could badly affect the intrgity of the Special Protection Area.
Mr Merricks is asking Her Honour Judge Hamilton to sanction a full judicial review of Mr Darling's decision, but the application is being hotly opposed by the DTI, represented by Richard Drabble QC, and Npower, represented by William Norris QC.
STRAND NEWS SERVICE