A British charity worker kidnapped and held to ransom in Nigeria was shot dead moments after singing Amazing Grace to a group of missionary medics, it has emerged.

The final moments of the life of Ian Squire were described by his fellow Christian missionaries David and Shirley Donovan, who were held alongside Squire and Alanna Carson after being abducted in the southern Delta state.

Donovan told the Daily Telegraph how the group’s spirits were lifted when the kidnappers returned a guitar and Squire started to play Amazing Grace.

“It was the perfect song, and at that point things began to look not quite as bad,” he said. “But then, after Ian finished playing, he stood up, and a salvo of gunshots killed him instantly. We didn’t see who did it, but it was obvious that someone in the gang had shot him. It was terrifying to see.

“We jumped out of the shack and into the water as we thought they were coming for us next, but a member of the gang came and put us back in there with Ian for the rest of the day.”

Donovan, 57, and his 58-year-old wife started the medical charity New Foundations in 2003. They said it was their Christian faith that kept them going after early setbacks including severe illness and thefts.

During their kidnapping, the group kept their spirits up by playing a version of the BBC Radio 4 quiz The Unbelievable Truth, where contestants have to tell fact from fiction, with Shirley Donovan saying the game was “prosaic but comforting”.

The captives were freed after the kidnappers told them a ransom had been paid. Donovan said the smell of the leather and air conditioning in the two SUVs that came to pick them up “was like stepping from one world into another”.