Exactly 31 years ago to the day, two Kenyan pilots, Hussein Mohamed Anshuur and Mohamed Adan, received an unexpected visitor at their office at Wilson Airport near the capital, Nairobi.

It was a Nigerian diplomat, who drew them into a sensitive and secretive mission to fly the body of Somalia's former ruler Siad Barre back to his homeland for burial following his death in exile in Nigeria at the age of 80.

Anshuur, previously a captain in the Kenyan Air Force, and Adan are partners in Bluebird Aviation, one of Kenya's largest private airlines that they had set up a few years earlier.

Speaking to the media for the first time about the mission, Anshuur told the BBC that the Nigerian diplomat came "straight to the point", asking him and Hussein "to charter an aircraft and secretly transport the body" from Nigeria's main city of Lagos, to Barre's hometown of Garbaharey in southern Somalia for burial, on the other side of Africa, a distance of some 4,300 km (2,700 miles).

Anshuur said they were stunned at the request: "We knew immediately this wasn't a normal charter."