They were in the Valle dei Nuraghi – the Valley of the Nuraghi – a wide, volcanic plain, baking under the burning sun. It was studded with the cones of long dead volcanoes and, as James looked more closely, he realised that there were several more of these mysterious ruined towers dotted about the valley like broken teeth.

They had left Dover five days ago, crossed the Channel by ferry, then travelled by train down to Genoa in northern Italy, where they had boarded a steamer for Sardinia.

A bus had been waiting for them in the port of Terranova, manned by a burly, dark-skinned Sardinian called Quintino, who was to be their driver and guide.

They had driven westward across the island to Torralba, through countryside that was wild and open, with not a building in sight. Its only inhabitants were flocks of sheep and goats being looked after by craggy shepherds in sleeveless sheepskin jackets.

They had settled down for the night in a local school, sleeping on army-issue camp beds under dusty mosquito nets. This morning they had driven out to the Neolithic site, which was looked after by a gnome-like man wearing the traditional local costume of loose-sleeved white shirt, black waistcoat, full white trousers bound tightly below the knees with black gaiters, and a wide belt with a sort of short black skirt, or apron hanging below it. On his head he wore a black stocking cap. He had folded the long flap, which would normally have dangled down his back, forward over his forehead so that it shielded his eyes from the fierce sun.

The site was dominated by the huge central tower, but clustered around it, and encircled by a low drystone wall, were the ruins of what looked like a whole village of small houses and huts, mostly circular in design.

Haight explained that the boys would be helping to excavate a roped-off patch of land outside the wall, digging in the dirt with small trowels and sifting it with sieves. A makeshift canvas awning had been erected among the thistles and corn stalks and underneath it were two long tables. Haight showed them the various artefacts that had been unearthed so far – fragments of pottery and a small bronze figurine.

‘These bits and pieces have been buried under the ground for centuries,’ he said, delicately turning a piece of broken pot in his hands. ‘I don’t expect we’ll dig up anything that will shake the world, but I wanted to give you boys a taste of what archaeology is all about.’

A serious young man from the local museum was supervising, sweating heavily in a dark suit. He seemed nervous and slightly miserable, obviously worried that the clumsy boys would damage something.

As James bent down for a closer look at one of the objects, somebody gave him a shove from behind and he sprawled across the table, knocking over the figurine.

The museum curator tutted and James spun round angrily.