In 1988, Dumfries and Galloway police is the smallest force in the UK: only 310 officers. Now they’re dealing with the world’s biggest crime scene.

Detectives from all over Scotland are bussed into Lockerbie overnight. Within days, American intelligence agents make an appearance. They hole up in Lockerbie Academy, each claiming a classroom.

Scottish police are determined to recover every single piece of evidence from the 845-mile crime scene. They bag everything that looks like plane debris before sending it off for forensic evaluation.

The investigation rolls on for two years, spanning Germany, Sweden, the UK, and Malta, a small Mediterranean island between Sicily and Libya. That’s when they make a series of breakthroughs.

Myles Bonnar speaks with investigators in Scotland and in the FBI about a Libyan double agent, dubbed Puzzle Piece. Could he unlock the whole investigation?

Lockerbie is produced by Caitlin Smith

Additional production by Rob WilsonSound design by Eloise WhitmoreStory consultants are Innes Bowen, Jack Kibble White and Graham RussellFact checking by Faisal QureshiResearch by Rachael O’Neill and Callum McCulloch-NowlanExecutive Producer: Gillian WheelanOriginal development by Sally Greig LockwoodBBC Scotland commissioners: Heather Kane Darling and Victoria Easton-RileyFor BBC Radio 4, the commissioning executive is Tracy Williams, and commissioning editor is Dan Clarke.Music by Callan Marchetti