At 7.28am on July 1 1916 Captain James Young of the 179th Tunnelling Company, Royal Engineers, set off 60,000lbs of ammonal placed beneath German trenches south of the French village of La Boisselle. The explosion created an immense crater thought to have obliterated as much as 400 metres of the defences and all those sheltering within them. It signalled the beginning of the "Great Push" that many were confident would end the war. The attack's success was supposedly guaranteed. It was expected that following seven days of intense artillery bombardment the enemy's trenches would have been obliterated and their barbed wire cut.
In fact, the German troops in their deep dugouts had survived. As heavily laden troops advanced across No Man's Land, German machine guns opened up on them. The same story was repeated along much of the British northern sector of the 15-mile Somme.
It was the start of the bloodiest day ever experienced by the British army. By nightfall more than 19,000 officers and men were dead and more than 34,000 wounded. The Lochnagar Crater still exists. Tens of thousands visit it every year to peer into its depths and walk around its immense rim. Ideally they will leave with some sense of what occurred there.
"Frustratingly, this is not always the case," says Andy Thompson headteacher of Oakwood School, Dorking. "I remember watching one group of children emerge unsupervised from their coach, complete a 10-minute circuit of the crater before leaping back on board for their next destination. Just one child took his time and stopped to write in the visitors' book. I was intrigued and went to read his comment. 'Very realistic', he'd said."
Nearby, the Thiepval monument is as eerie and mysterious a site. On it are engraved the names of more than 72,000 men who died on the Somme but whose bodies were never recovered. The spaces defined by the arched structure suggest this collective "lack" and from its elevated position it is possible to survey the slopes up which British troops had to struggle towards the German positions.
Sadly such subtleties are lost on the vast proportion of visitors. Apart from being confronted by the monument they have nothing to explain its significance or the context within which the suffering and sacrifice it commemorates occurred.
This is about to change. The land for a visitor centre behind a screen of trees adjacent to the monument has been secured. The ground has been surveyed to ensure it is free of dugouts or unexploded ordnance (a third of the shells that fell on the first day of the Somme were duds). And the pound;1,120,000 cost is well on the way to being met thanks to energetic fundraising in the UK and a generous offer of matched funds from the local French commune. All that remains is to decide what exactly to put in it - what interpretation it should offer.
Over the past 10 years there has been a substantial rise in school visits to the battlefields of France and Belgium. Alain Chissel, of Anglia Battle Tours, says: "While many are well-organised and carefully designed to maximise the impact of the experience, an increasing number are being put on by coach companies eager for bookings in the otherwise slow months of October and November. A good battlefield guide is essential. We use a number of ex-soldiers - people who can really convey what it is to be frightened or to fix bayonets and for whom the slightest fold in the landscape is significant."
Military history specialist Richard Holmes says: "However passionately I talk to a school about the First World War, I am always up against Wilfred Owen." He is not alone in finding the view of the war as mediated by Sassoon and his protege unhelpful in dispelling its myths or conveying the attitudes and experience of ordinary men called upon to fight.
"For the majority, the war was worthwhile," says historian Dr Gary Sheffield. "German militarism needed to be defeated and the idea that it was a conflict in which lion-like soldiers died because of the callous indifference of ignorant donkey staff officers is wrong."
His best seller Forgotten Victory (Headline) spells out how the generals were fighting a new kind of war - one that relied on attrition and during which they displayed considerable capacity to learn and experiment.
"In 1914 the army had its roots in the Crimea, by 1918 they were anticipating Blitzkrieg with tanks and aircraft and much improved field communications at their disposal," he says.
In keeping with this interpretation - the July-November Somme campaign, while not a victory, was a success, bringing about a growing understanding of the use of creeping artillery barrages as an adjunct to infantry attacks on defensive positions and causing the Germans significant losses.
"What we need to do," says Thiepval Project chair Sir Frank Sanderson, "is to provide a sense of why the war occurred and what its aftermath was. It must also give some much-needed balance to the other numerous visitor's centres that dot the Somme and other First World War battlefields. Many of these - such as the one in the Newfoundland Park at Beaumont-Hamel or the Ulster Tower describe the contribution of the troops of single nations or regions often over quite narrow periods of time and leave the visitor with little purchase on the broader scheme of things."
Another model is the kind of take on the War provided at the Historial Museum in Peronne which boasts a powerful collection of images including Otto Dix's "Der Krieg" drawings. Here the European Union message is to the fore with everything explained in German, French and English and displays attempting to provide somewhat reductive snapshots of the cultural context prevailing in each nation on the eve of war - Prussian duelling swords opposing English cricket bats and rowing oars.
The museum also boasts a nice line in beautifully laundered uniforms. Sanderson is cool about such artefacts and is keen that the Thiepval centre avoids displaying the kinds of rusty finds that still emerge in huge quantities from the Somme fields after ploughing or heavy rain. "Getting it right is a significant challenge and it is inevitable we will not please everyone," he says. "What is important is ensuring that children going to Thiepval are not left with the same confusion of one youngster I met on a trip to the battlefields who turned to me and asked whether or not the British had played a part in the war."