“I am confident that he is here. Are we in exactly the right place? That’s a different matter.”

Jon Hill overlooks a bleak bog on a windswept hillside in Co Monaghan not far from the Border with Tyrone. It looks like a World War 1 battle site with tree stumps, mounds of turned earth and shallow trenches. Yet, as the digging machinery and the searchers clad in high-visibility gear demonstrates this is very much a 21st century scene. The people working here are trying to write what is hoped will be the final chapter of one aspect of the Troubles.

They, like Mr Hill of the Commission for the Location of Victims’ Remains, are searching for the remains of Columba McVeigh who was abducted by the Provisional IRA in 1975, murdered and secretly buried somewhere at this desolate spot. He was 19.

Mr Hill, a former senior detective in England, has worked on searches for many of the so-called Disappeared – those taken and killed by proscribed organisations and whose bodies have never been found. But the searching goes on and Mr Hill has helped uncover the bodies of Danny McIlhone, Gerry Evans, Charlie Armstrong and Peter Wilson and return them to their grieving families for Christian burial.

He oversees the dig, helps analyse the intelligence given to the commission by former paramilitants and liaises with the families who still grieve for their lost ones despite losing them nearly 40 years ago.

Despite the awfulness of the events which led to this, Mr Hill speaks only in human terms about the task before him. It is an issue of simple humanity, not politics or security or threats to the State.

“I believe that the people providing us with the information are doing it for the best reasons with the best will in the world,” he says of former IRA contacts now striving to piece together the last, presumably awful, moments in the short life of Columba McVeigh.

He says he has “good relations with them” but recognises that acquiring reliable information about a death in 1975 is “a slow process”.

“Often a sound tip-off is followed by a counter-reaction,” he says which means that things can go cold for a while. But the case book is never closed.

The site was first examined by Garda officers in 1999 and again the following year.

New information was supplied two years ago and was thoroughly tested for 12 months before searching began in earnest.

This is a restarted search, postponed since last October with the onset of winter and long nights. Unlike what many would suspect, this is no hit-and-miss affair but a targeted search based on (hopefully) hard evidence and reliable intelligence.

The McVeigh case was reviewed in 2004 and a series of high-tech technologies incorporated into the hunt for his body.

Working here are expert geophysicists trained in identifying land that has been turned over – even as far back as 1975. Alongside them are imaging experts, who plot the site and examine it for signs of human interference; forensic archaeologists and handlers of so-called cadaver dogs which can help uncover human bones even after decades.

Controlling the diggers are experts who can scrape away the peat just a few centimetres at a time. Their huge machines are positioned on steel 3-metre by 4-metre platforms to prevent them sinking as they work. Any evidence of a make-shift grave will mean the rest of the dig will be done carefully by hand. It is slow and detailed work done by men and women provided with the most frugal of comforts – a mobile hut, portable toilets and a diesel generator.

Their skill appears matched only by their patience.

“If he is here and we’re searching in the right place then we will find him,” says Mr Hill. “There is no chance that we are going to miss him in one of our searches.”

Meanwhile, the McVeigh family waits another day for news as they have since 1975.

Information can be supplied anonymously to the Independent Commission for the Location of Victims’ Remains on freefone 00800 55585500.