AT 7.30 this morning, the blast of whistles will pierce the air in the Picardy countryside, marking the 90 years since the moment that thousands of soldiers were ordered out of their trenches at the start of the bloodiest day in British history.

Yesterday, on a day as hot as July 1, 1916, children of the late 20th century stood on the rim of a huge British landmine crater on the German front line at the village of La Boisselle. Sappers detonated the huge “Lochnagar mine” under the German trenches there as the advance on the Somme began. Looking across the wheatfields and poppy-lined lanes yesterday, youngsters said that it was almost impossible to imagine the butchery of that morning.

The men of the Tyneside Scottish and Irish, barely older than them, walked like a football crowd up the fields into the line of fire of German machineguns to be “mown down like corn before the scythe”, as a survivor put it.

“People just wouldn’t do that any more. It was like committing suicide,” said Steven Harper, 15, who is on a school trip from Bradford. Linking the young generation to the scale of the 1916 tragedy is a central theme of this year’s commemoration now that the Great War has almost passed from living memory.

Teenagers are taking part in the morning ceremony, attended by the Prince of Wales, at the Thiepval monument.

Among the boys is Harry Shuell, 14, from Bury Grammar School, in Greater Manchester. He is to read Rupert Brooke’s The Soldier, but yesterday he went in his Cadet Corps uniform to lay a wreath at La Boisselle for a great-great-uncle who was killed there at the age of 25. Birds sang in the rebuilt red-brick village as Harry mused on Private Thomas Seville, of the King’s Own Royal Lancaster Regiment, the ancestor whom he had only recently discovered and whose name is one of the 70,000 missing inscribed on the Thiepval Arch.

Tom Filer, 18, also at the Bury school, said: “The thing that hits you is that they were men our age. We are always commemorating the old boys but you realise that they are people who just finished their studies and went off to war.”

Tom, who wants to join the Army after a degree at the University of Exeter, will also read a poem at the ceremony. Bury Grammar School was chosen because its old boys paid one of the heaviest prices of the war. Of 165 who were at the school in 1914, 97 were killed in the First and Second World Wars, many of them in the pals’ battallions of the Somme.

“Those figures show the scale of the sacrifice,” Mark Hone, a teacher leading the Bury group, said. “A lot of the boys became officers and sergeants who led them over the top. Now we are putting names and faces to them all.”

As Mr Hone was talking, an elderly resident of the village handed two 1916 copper shell noses, found near by, to the visiting group. Every year farmers and residents turn in about 50 tonnes of ordnance and other debris from the fields where the remains of 70,000 allied servicemen lie.

Emphasising the scale of the tragedy is a goal of Richard Dunning, a Briton who bought the land of the Lochnagar crater in 1978, when it was threatened with being filled in. “On every coach there is a kid who is really touched by it all. If we can reach just one kid it is worth it.”

Yesterday Britons, Canadians, Australians and others from the Commonwealth toured the cemeteries scattered along the 25-mile (40km) lines of the 1916 battle. Vehicles jammed the lanes in one of the biggest influxes of Britons for decades. But for the first time there were no veterans of the battle.

One of the most moving memorials is the stretches of frontline trench in the Thiepval wood that have been restored since 2004 by the Somme Association. The Duke of Gloucester is to dedicate the wood and its excavated trench as a memorial park today.

Another stretch of trench was on display behind “Avril’s Tea-room”, a British-owned café in Auchonvillers, a battlefield village near Thiepval that the 1916 Tommies knew as “Ocean Villas”.

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