John and Jane Martin lost their second son in an accident in Pakistan but the tragedy changed their lives in a radical way.
Samuel was 25 years old when he fell and died while on a mountain trek in the north of the country in 1988.
When John and Jane went to visit their son's grave, they found their previously held assumptions about Muslims challenged by the comfort and support they received.
"When I visited Samuel's grave in Gilgit I met some kind Muslim friends and we drank tea together," recalls John, who works at Christian charity Counties.
"They comforted me and said: 'His death is the will of Allah: accept it and be at peace.' I was grateful for their friendship and compassion.
"We also met some Christian friends who showed us a beautifully written prayer hanging on the wall. It said: 'Father I do not understand you but I trust you.'"
That experience helped John to hear God's special message to him - that Christians should not be afraid to talk with Muslims and they should be friends.
This message inspired John and his wife to befriend Muslims in their area. They also regularly travel on London buses, sharing stories of Jesus with Muslim passengers.
The pamphlets they hand out, 'The Common Ground and the Great Invitation,' have proved to be very popular.
"We have come to understand that our Muslim friends share many of our beliefs, but their legalistic spirit prevents them from understanding God's grace and forgiveness," says John.
"We have discovered how much they enjoy the gospel stories of Jesus welcoming sinners."
For the last two years, John has attended a lunch with Muslims organised each month by a Muslim seeker.
The get together is more than a social occasion as they read and discuss the Bible and the Koran.
John adds: "We need to listen to each other, affirming what is good and true. Christians and Muslims actually have more in common with their beliefs than many people realise.
"It's always best to establish common ground, in order to talk about our vital differences in a friendly way."