‘Another three cores and we’ll be almost at the edge of the bog,’ he observed, as he screwed together two sections of metal tube about the thickness of a walking stick.

Louise looked up and nodded. ‘We’ll pack it in then and after we’ve checked the results from this lot, see if the professor thinks that would be enough.’

They were engaged on a study designed to see how the bog’s vegetation had changed over past centuries and relate this to its topography and the climatic variation. Taking samples of the underlying peat from different depths, an analysis of pollen grains and plant remnants should reveal the sequential history of Cors Fachno, the true Welsh name for Borth Bog. The samples were retrieved with the simple coring apparatus that they were now assembling.

‘I’ll soon be doing this in my sleep,’ grumbled Geraint, a thin, tousle-headed youth, dressed in a tweed sports jacket with frayed cuffs, over a purple pullover and corduroy trousers.

He jammed the sharp bottom end of the long tube into the ground and pushed it down hard so that it stuck in securely without support. Reaching up, he screwed the central socket of a wooden cross-arm on to the top of the tube. As he pulled down again on this, his wellington boots sank a couple of inches into the waterlogged heather and spongy moss. The three-foot wooden bar, now making a spindly T-shape with the tube, came just within reach of Louise’s hands and she reached up to grab one side, with Geraint on the other.

‘Right, let’s pull!’ she commanded and they both added their weight to the contraption to drive it deep into the soft marsh. The object was to force a narrow cylinder of soil up the inside of the tube and, normally, they could get down to the full length of six feet with steady pressure. However, this time the tube went down as far as the joint at the three-foot level and stopped abruptly.