Markwells Wood, west of Chichester, is 11 hectares of peaceful, beautiful, ancient woodland, sitting within the South Downs Area of Outstanding Natural Beauty (AONB), and the proposed South Downs National Park. It is surrounded by a handful of small residences and the lush green fields which typify this part of the UK.

Later this year, Northern Petroleum, a gas and oil exploration company, will begin to clear one hectare of the wood's irreplaceable ancient soils. Then it will cover the land with 30cm of stone and erect a 36m drilling rig in an attempt to find a share of 200 million barrels of oil thought to lie under the Weald Basin of Hampshire, Surrey, Sussex and Kent.

Northern Petroleum's planning permission allows the company to be there for three years, at times drilling for 24 hours a day and, if the exploration is a success, it will seek to build more rigs throughout the woodland.

Mick Hodgson is the chairman of the planning committee for West Sussex County Council (WSCC). He says: "There is a very strong presumption in favour of allowing oil exploration which comes from central Government. There is a heavy steer to allow it to happen for energy, security and economic reasons."

But, in this instance, the land in question is in an AONB, the highest possible grade of land protection next to being a National Park and, regardless of pressures from above, the committee has a duty to show there is a clear and overriding need for this development.

Northern Petroleum estimates the Markwells Wood site has 27.5 million barrels of oil in place. This is the total amount of oil and oil equivalent held in the reservoir. Not all of this is recoverable.

Normally only between 30 to 35% of oil in place can be extracted, which here equates to a maximum of about ten million barrels - enough to last the UK less than a week, given its current oil use of 1.87 million barrels a day.

A less optimistic prediction comes from Black Rock Oil and Gas Plc, which has a 10% share in the site, and says there could be between three to nine million barrels. But at the upper end of the scale, and with the price of oil reaching a record £62 a barrel last week, it is still enough to bring in £620 million for the stakeholders.

So does one week's worth of oil constitute a clear and overriding need?

Mr Hodgson says: "We don't know - and I have no idea. It wasn't even brought up in the meeting how much oil is available in that location. But the clear direction from central Government is every little bit ought to be used.

I'm not an expert in oil. I know virtually nothing about it. I'm sure the applicant has done sufficient homework. These wells are not cheap. They are not going to stick a borehole in the ground unless there is something worth having."

Except Northern Petroleum has already done just that.

In October 2005, they halted exploration at a site on the Isle of Wight - vacated by British Gas some 20 years ago - after no oil was found. The oneyear search cost the company and its partners more than £2 million and MD Derek Musgrove admitted the predictions were badly wrong.

It also seems oil is not the only thing the WSCC planning committee has chosen to know nothing about.

When asked about destroying an ancient woodland, Mick says most members of the committee visited the site and saw the oldest trees were 30, maybe 40, years old and were only conifers at that. He said: "We decided the woodland was not as important as doing the oil exploration."

But a spokesman from the Woodland Trust angrily branded him as "ignorant", explaining that 500 years ago, the area was typical ancient woods, with mixed broadleaves and a rich, diverse ecosystem. In the 20th century all the broadleaves were taken out and conifers planted instead.

"The ecology of the ground went into stasis," he says. "So although the trees on top are different, the soils are the same. If you were to cut down the conifers it would regenerate into ancient woodland - more things live in it than above it. By walking around you wouldn't know that. You can't just say, Ooh yeah, conifers'. That is not looking at the details."

The environmental report from Northern Petroleum says it will store the soils and return them when they are finished. The Woodland Trust is not impressed. "This is one of the most complex ecologies in the UK and it relies on being undisturbed," the spokesman says. "Take it away and it's gone forever.

"Is the council even listening to its own ecologist and landscape officers who explained this and said the planning application should be rejected? No, they just went up there and looked at conifers."

Wider concerns come from the Transition Brighton and Hove environmental community group.

Doly Garcia is coordinating the creation of an Energy Descent And Resilience Action Plan, a document which will set out ways in which the city can move from a high-carbon to a low-carbon economy in the face of climate change and dwindling oil supplies.

She says while it may make Northern Petroleum a large profit, in the grander scale of things it is diverting attention from a much needed solution to the coming energy crisis.

She says: "The numbers may look big but compare it to UK consumption and the decline in North Sea oil and you realise it is actually very little.

"I would compare it to a time when everyone in the UK was cutting down trees to use as firewood, then they were running out of trees and no one knew what to do. So they started using coal and, of course, that came with its own problems but it led to the Industrial Revolution. Other countries weren't keen and they were left behind. This is the same situation.

"If you try to stick with forms of energy that aren't working, you get left behind. Oil production is declining across the world and there is no avoiding that. Trying to produce a little more from smaller fields is not going to solve the problem."

Despite assurances from WSCC that the licence is only for three years and the disruption and damage will not be permanent, there seems to be plenty of evidence this is not the case.

Markwells Wood is the first of two rigs Northern Petroleum plans to set up - the location of the second is yet to be announced - and if commercial quantities of oil are found, then further drilling will be needed, giving rise to fears from objectors it could lead to the destruction of the whole 11 hectares of wood.

Of course, the company will have to apply for permission to do this. But Mick Hodgson does not seem to think any of it is a problem.

He says: "If they do find oil, then they will extract it. There are two working oil fields in Sussex already.

It's not unique. The committee feels comfortable doing this."

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