Edgcote, Northamptonshire: the Wars of the Roses battlefield lies on the line of the HS2 rail link. Photograph: Colin Underhill/Alamy
To archaeologists, the HS2 high-speed rail scheme is "one huge trench across the country", an unprecedented 350-mile bonanza that promises to open up England's ancient backbone and shoulders for meticulous study in a way never before possible. To many historians, however, it is a colossal folly, an unwarranted assault on the nation's historic heartlands that will dislocate a wealth of precious links with the past.
Even supporters of HS2 concede that the cost to heritage of building the line is likely to be high. Opponents see the resulting gain in travel time, expressed as minutes here and there, set against centuries lost to the bulldozer.
If it goes ahead, HS2 would pass through an extraordinary range of historic landscapes, from inner London Victoriana to home counties Tudor and Elizabethan, then on to Midlands medieval and industrial, and northwards to houses and gardens in the grand style. And everywhere there is archaeology, much of it untouched and so far largely unidentified, the shards and stones of pre-Reformation and ancient Britain.
Yet, despite widespread awareness of the importance of this rich seam of history, English Heritage, the government's adviser on the historic environment, has issued a highly critical report on the heritage assessment work being carried out by HS2 Ltd, the company set up by the government to oversee the delivery of the line, before work begins. In its recently published response to the environmental statement on heritage affected by phase one of HS2, prepared by HS2 Ltd as a statutory requirement, English Heritage attacks the quality of historic environment assessment work by the company.
It criticises HS2 Ltd for failing to carry out essential fieldwork, without which "it is impossible for us to assess" what remains may be in danger: "We consider there is a realistic likelihood that archaeological remains of national importance… will be affected, but have not yet been identified and described."
Singled out for criticism by English Heritage is HS2 Ltd's lack of detailed work on the historic environment in the Chilterns, an area of outstanding natural beauty and an archaeological hotspot. "Discussion of it is limited to two paragraphs, and the impacts on it limited to three," says English Heritage.
Buckinghamshire county council estimates that some 7,000 designated heritage assets will be affected by the London to Birmingham phase of HS2 alone. This includes ancient field boundaries and tracks, historic buildings, hamlets, villages and major archaeological sites. The actual number at risk could be far higher, since that figure excludes historic buildings, sites and remains which have no statutory protection – a large proportion of them.
English Heritage has identified a series of listed historic assets of national importance that would be destroyed or badly affected by the first phase of construction. In Camden, north London, where a new terminus for HS2 is proposed for Euston station, English Heritage mentions St James's Gardens burial ground and park, last resting place of some 50,000 Londoners. Other places of concern include Doddershall medieval village site in Buckinghamshire, and a Roman villa and a wars of the roses battlefield at Edgcote, Northamptonshire, along with medieval farmhouses and pre-Roman sites.
Also highlighted in English Heritage's response is Grim's Ditch, a large, ancient earthwork skirting Wendover in Buckinghamshire. Despite scheduled monument status, HS2 would run through it, destroying a 150-metre section.
But the actual toll could be far higher than the English Heritage list suggests. Opponents of HS2 argue that the "damage zone" extends far beyond the immediate vicinity of the high-speed lines, unpicking in a few years a delicate fabric formed over centuries. Warwickshire county council calls the impact of the scheme "devastating on our countryside and our communities".
"This landscape has survived as it was since at least 1620," says writer Alison Doggett, an expert on the Chilterns. The region, much of which is statutorily protected, will be cut through by HS2. Tunnels will hide a proportion of the line, but one historic area, the Missenden valley, will be dissected diagonally by miles of concrete viaducts and embankments.
"I have matched a map from 1620 against the valley as it is now and, astonishingly, the patterns are there, exactly the same – the hedges, the fields, the lanes," says Doggett. "Under HS2 they will take these tiny lanes, with high sides, tree tunnels, some of them Anglo-Saxon, and are going to widen the roads and rip out the hedges and the banks, for lorries. There are three lanes in particular they're going to remove, which are all on the 1620 map. Once they're gone, they're gone."
Less than two miles from the Missenden valley – but sheltered by a ridge from construction work and near-perpetual train noise – is Chequers, the prime minister's country retreat.
Opponents of HS2 believe that the heritage risk assessments are flawed. "This area is an AONB – that's national heritage, the whole area, and it all hangs together as a mosaic," says Steve Rodrick, chief officer of the Chiltern Conservation Board. "It's the sum of its parts. The government doesn't understand that. "It doesn't understand that heritage is a lot of inter-relationships with a time depth. It's fragmented all those elements. The Chilterns are a national asset and we are all stewards of a national treasure, and the ultimate responsibility, ironically, rests with government and parliament. Yet they are failing in that stewardship."
But not all professional historians are wary of HS2. "From an archaeological point of view, this is an opportunity," says Dr Mike Heyworth, director of the Council for British Archaeology. He sees HS2 as a "huge trench across the country where we can learn an awful lot about new sites. As long as the procedures are followed properly and the archaeologists are given enough time on site and there are adequate resources to do their work, that shouldn't be a problem. We're in touch with HS2 Ltd and have been involved with them in high-level negotiations and discussions, principally about routes, at a local level. This is the largest-ever opportunity for archaeological investigation in one go."
Dr Heyworth acknowledges that the prospect of the unprecedented tidal wave of archaeological work which would arise from HS2 – against the clock, on a tight budget, and amid unprecedented cuts in funding in the heritage sector – would place a severe strain on the profession.
"There will be a shortage of skills and manpower. There's been a shrinkage in the number of professional archaeologists, and a loss of skills. And if suddenly we're getting a lot of new housing and building development, we're going to run out of archaeologists. We won't have the skills base we need to do a professional job.
"One solution may be to bring in archaeologists from other parts of the world, and certainly our colleagues across Europe are very well trained and experienced. There are some who would argue that you don't need that academic background... you don't necessarily have to have a great deal of experience of that as long as you are well supervised."
Others are unconvinced that HS2 will reveal anything that would not eventually come to light. "This archaeology work would be done anyway, without HS2," says Rodrick. "We know there is stuff we have yet to discover, but at least we've got the luxury of time. The archaeology is safe where it is."
A spokesman for HS2 Ltd said: "We fully understand the value of our heritage and have avoided sensitive sites where possible. Grim's Ditch is the only scheduled monument the railway will affect between London and Birmingham and we are working with English Heritage to minimise the impact there.
"HS2 will be the largest archaeological dig the UK has ever seen, offering an unprecedented opportunity for ground investigations along the 350-mile route in the same way as those carried out on HS1 and Crossrail. The environmental statement includes a wide range of measures to blend the route into the existing landscape."
Environmental factors arising from HS2 are being used by opponents to take the fight against the £50bn scheme beyond the UK for the first time since the line was proposed four years ago. The campaign group HS2 Action Alliance will this week make a formal complaint to the Geneva-based compliance committee of the Aarhus convention – the international agreement aimed at limiting environmental damage caused by major infrastructure schemes – to which Britain is a signatory.
Two months ago the alliance's case that the government had broken the law by not initiating a strategic environmental assessment (SEA) for HS2 was rejected by the supreme court. SEAs are enshrined in European law, a well-known and long-established element of environmental protection legislation and procedure. HS2AA contends that the court's decision leaves the UK in breach of its treaty obligations under the convention.
"The environmental impacts are off the scale. It's hard to envisage how destructive HS2 is," alliance director Richard Houghton told the Observer.