Housing developments are having a major effect on leafy Sussex's scarce ancient woodlands.

Passengers on trains racing through Haywards Heath hardly get the chance to glance at Ashenground Wood as they speed past.

But any travellers who did would, until recently, have found one of the richest surviving pieces of ancient woodland in Sussex.

Home to such rarities as lobster moths, purple emperor and grizzled skipper butterflies, it survives in fragments as hundreds of homes are built where oak, maple and ash trees once stood.

Some of the trees in Ashenground Wood, and next door in Catt's, Pierce's, Eleven Acre and Orchard Woods, would already have been growing when the Romans built the road that runs through them.

Others would have been hundreds of years old when a later generation of engineers built the main London to Brighton railway line, taking a similar track through the countryside.

For many of the trees, and for the wild plants and animals they supported, the last gasp came as the area became another casualty of the South-East's insatiable demand for new homes.

Losing so much of the old woods has dismayed conservationists and sent a warning to people elsewhere in the county fighting to fend off similar developments.

John Sampson, of the Friends of Ashenground Wood, said: "It was like something out of a Chekov novel, it was really beautiful. It is gone now - it is tragic.

"This is now an exercise in damage limitation but others could learn from it and really learn the lesson."

West Sussex needs to build 20,000 homes on greenfield sites between now and 2016, about half on land already earmarked by district and borough councils.

Ashenground Wood, butting the south-west corner of Haywards Heath, is among the sites already identified.

Eventually there will be 780 houses at Ashenground and on the surrounding woods and fields, of which 187 already have planning permission.

Most of the latter are part of the new village of Bolnore.

The first anybody heard that Ashenground Wood was to be built on was in 1995. The news prompted Roy Horobin to organise a public meeting, which more than 100 people braved the January weather to attend.

Mr Horobin said: "I turned up at the council room and, to my amazement, the room was full and people were standing all the way down the stairs."

They formed a campaign to save the woods, mounted demonstrations, organised petitions, argued with the district council, went to Parliament to lobby MPs and environment ministers. But they failed to stop the plans.

Mr Sampson said: "What it is is a war of attrition. They grind you down with protocol. It is like fighting fog. They have this strategy and they will bulldoze it through whatever happens.

"It is a salutary warning because once it is gone it is gone forever."

Follow the route of the Roman road south from Haywards Heath, cross the South Downs, and you will eventually come to another piece of ancient woodland threatened by new homes.

Titnore Wood, in the lee of Highdown Hill at West Durrington, near Worthing, and on the edge of the proposed national park, is one of only two ancient woodland complexes left on the Sussex coast.

It is the target for more than 800 homes, plus an industrial development. A public inquiry on whether they can go ahead is due to publish its findings in a few weeks.

Campaigners have already formed Protect Our Woods to try to stop the development, mirroring what has happened at Ashenground Wood.

Environmental politics, however, have moved on and there is likely to be more militant opposition.

Campaigner John Hughes said: "I think there is going to be severe pressure on them.

"There is already talk of Swampy-type people turning up to protect the trees.

"There is also talk that people want to declare independence from West Sussex and set up an independent state of West Durrington. People are very angry.

"They (the developers) are talking about new planting and the like. If they can replant ancient woodland, something that has taken thousands of years to mature, I would be surprised."

Tony Whitbread, head of conservation at the Sussex Wildlife Trust, who intervened to try to get better protection for plants and animals at Ashenground Wood, said there were similarities between the two areas.

He said developers did try to lessen the damage, by building buffers between woodland and homes and putting wildlife corridors between the best sites, but when ancient woodland was felled, or habitat became too fragmented, it could not be replaced.

He said: "Developers are not all terrible. Nevertheless we should not be making decisions like this nowadays.

"In future I would hope we would find strategic locations for development which would not affect such important environmental assets.

"We should not be taking decisions to put major areas of strategic development in areas that are going to affect ancient woodland."