It will be a time and date nobody working in the emergency services will forget. Only four short days before Christmas 1988, police, fire and ambulance units from northern England and across much of Scotland were rushing to a tiny town in Dumfriesshire to help in the immediate aftermath of the crash of Pan Am Flight 103.

At 7.03pm on Wednesday, 21 December, the Boeing 747 jumbo jet, known as Clipper Maid of the Seas, exploded over the town of Lockerbie. The devastation was extensive. Homes were destroyed, cars damaged and 11 residents lost their lives.

What is known now - that a bomb was planted in the cargo hold of the plane by Libyan agents - was far from the minds of those seeking to comfort the people affected by the tragedy.

The Chief Constable of Dumfries and Galloway Constabulary – Scotland's smallest police force – was to lead the investigation. John Boyd help lay the foundation for what would turn out to be a meticulous evidence-gathering process that required the help of the world's leading intelligence organisations to finally bring the people responsible for the incident to justice.

In a hastily called press conference on the night, the chief constable provided the first official description of the disaster and the ongoing search operation for victims. The swelling numbers of reporters wanted to know what had happened, as well as details about the plane's passengers and the people in Lockerbie affected by the incident. Constable Boyd took a cautious approach to reveal only what was known in those early hours of the investigation.

Although it would take nearly three years to issue the first arrest warrants for those linked to the bombing of the plane, it would take many years of work in crime labs and in the courts before a conviction could be made.

It all started on a cold and damp night some 20 years ago in what would become Scotland's worst disaster in modern history.