A cry of triumph rose up from the western end of the dig, closest to the Abbey ruins. As soon as she heard it, Hannah dropped her trowel, blinked for a moment in the woozy head-rush of standing up too quickly, then hastened over to where Magnus and the other senior members of the team, each with a telltale strap of sunburn on the backs of their necks, squatted around a trench. For once, she forgot about the creaky back that always played up after she spent too long crouching in the same position and made her first few steps into more of a waddle than a walk. This was not the moment to bother about that.

It was day four of the dig, and its leaders had known where to look from the end of day one. Once the mesh fence around the three abandoned tennis courts had been taken down and the top layer of asphalt, with its faded white lines marking out three forlorn sets of baselines, sidelines and service boxes, had been scraped off with a mechanical digger, they had embarked on the geofizz. That was what Hannah called it, after years of watching Time Team, but the professionals stuck strictly to ‘geophysics’. Whatever it was called, it involved an electrical probe to measure resistance, a magnetic survey to map all kinds of things in the soil, not just metal, and ground-penetrating radar. The whole process produced three different maps of the site which could be laid on top of one another, providing pointers for anyone skilled enough to interpret them. Hannah, who was one of the community volunteers welcomed onto the dig to maintain good local relations, could not tell one dark shadow from another, but she was digging alongside plenty who could.

Looking for a coffin-shaped object should have been easy, were it not for the fact that they were searching for it in a graveyard. For five hundred years, all the monks of an abbey the size of a town had been buried here, between the east end of the great church and the infirmary. They were not so much looking for a needle in a haystack, therefore, as a strand of hay. Fortunately, it was not completely hopeless. From what Magnus, the youthful volunteer coordinator, had explained, the monks tended to be buried in lead coffins, whereas the object they were looking for was a wooden ‘feretory’ – or portable shrine – adorned with gold and locked in an iron box. The iron would have disintegrated long ago, but the metal would leave traces in the ground that the geophysics could discern, and the gold adornments ought also to have survived.

Sure enough, the geophysics had pointed to the likely place, with iron traces delineating an area of the right shape and size, over by the remains of one of the little semi-circular chapels that protruded from the ruins of the presbytery. That location made logical sense: the monks had not had far to lug their sacred burden as they hurried to hide it from Thomas Cromwell’s sixteenth-century Taliban.

The discovery did not mean that Hannah and her colleagues could all simply pile in with shovels, like cartoon pirates racing to unearth a chest of doubloons. As Magnus never tired of repeating, this was a one-off opportunity for the site to give up its secrets before the ground was closed up again and it must not be squandered. There was at least half a metre of earth to be sifted meticulously before they got near the right level, and there was also the rest of the site to be investigated. ‘It’s an area of approximately one thousand square metres or, in layman’s terms, the size of three tennis courts,’ he said. Hannah laughed, but everyone else groaned.

She had been given a trench at the north-eastern corner of the site, farthest from the spot that looked so exciting in the geofizz. It was on a small brow before the land fell abruptly away towards the children’s playground and the tiny chalk stream that bounded the Abbey Gardens. This river had once been big enough to turn the mill that supplied the whole town with flour, and also to carry the great limestone blocks from the quarry at Barnack, on the other side of the Fenlands, with which the greatest church in Christendom had been built. Those blocks were all gone now, and all that was left of the abbey buildings were the misshapen lumps and towers of flint rubble that had formed the core of thick walls and soaring pillars. The little outcrop where she was working had most likely been built up at some much later stage to create a suitable plateau for the tennis courts. She would therefore have deeper to go before she reached anything interesting, but it also meant she was at less risk of doing any harm. In any case, she could hardly volunteer for a dig and then complain about the amount of digging she had to do.

It was warm work, with the permanent yeasty fug from the town’s Victorian brewery sitting heavy in the air. She fretted at first that she might miss something important, given that everything looked much the same when it was caked with earth. Under Magnus’ tutelage, however, she learned that there was no danger of that, provided she was painstaking. ‘Anything that isn’t earth is either a pebble or an artefact,’ he told the group of half a dozen volunteers, fiddling with his man-bun as he spoke. It had a habit of falling out and Hannah reckoned it needed a pair of chopsticks to secure it, but that would doubtless spoil the look. ‘Just make sure you sift every trowelful of earth and examine every object properly. Remember, your brush and your pail of water are your friends here.’

It was acceptable to hack at a decent lick through the topsoil, which was not so different to digging her own garden. After that, the earth needed removing layer by layer, with each few centimetres kept in its own bucket so you knew which order to put it all back. At her corner of the site, Hannah was following the line of the infirmary wall: to her great relief, no one had the slightest desire to open the monks’ graves, and it was the stuff around the outside of the cemetery that they cared about. At first she got excited at every piece of broken pottery, until she realised that she had yet to dig past the twentieth century. After that she reined in her expectations and could not quite believe it when she unearthed a copper belt-buckle, an iron key and a piece of yellow-and-black Cistercian ware which Vernon, the most senior archaeologist on the dig, identified as Tudor. She could see why people got hooked on this kind of thing.

She was so caught up in her own discoveries – the extraordinary thought that she was the first person in five hundred years to handle this shard of pottery or the lead bowl that she found an hour or two later – that she forgot all about the serious business happening over by the presbytery. Then came that exultant hullabaloo and suddenly she remembered again, and it was thrilling, like being in the Valley of the Kings when Carter and Carnarvon first gazed on the face of Tutankhamun. Hopefully their own find would not come with a curse.

Vernon and another of the proper archaeologists, a thirty-something woman with blue hair called Daisy, were down on the floor of the excavation, about a metre below ground level, with everyone else looking on, either crouched on their haunches or leaning into the pit. They watched as Vernon gently prised an object from the soil and reached for his brush to dust it clean. As he did so, it caught the light of the hot July sun with the unmistakable gleam of gold. Having brushed off the worst of the dirt, he now held it up for them all to see: it was a crucifix.

Meanwhile Daisy was digging on, carefully now, with a brush and the tiniest of trowels. ‘Vernon!’ she said urgently, and he turned back to see. Those crouching and craning above them collectively leaned a little closer too.

Vernon was using his brush now too, and it was hard to see what the pair of them were doing because first his head was in the way, then hers. Then they both sat back on their heels, revealing their find. A dozen diggers, professional and novice, gasped in unison, and one of the younger volunteers stifled what sounded like a sob. Hannah felt every tiny hair on the back of her neck stand to attention.

They all stared in wonder, and the half-buried skull that Vernon and Daisy had unearthed stared back at them, grinning.