The Bible Society's Diamond Geezer campaign is encouraging people to think about who they are indebted to - their 'diamond geezer'.
The campaign reflects the meaning of Jubilee in the Bible, a special year when wrongs were forgiven and debts written off.
The diamond geezer could be an old school teacher, a friend who was faithful in prayer, or someone who showed kindness or helped in some way.
Bible Society’s Richard Franklin said: "With our busy lives it’s often easier to send a quick 'thank you’ text, but we thought wouldn’t it be great to take the time and hand-write a letter to that person to thank them for everything they’ve done. After all who gets a hand-written letter these days?
"And it’s proving popular. Five hundred people have pledged to write letters in just a few days and we’ve had church leaders who say they’re planning to share the idea with the whole church."
Those taking part are being encouraged to go to biblesociety.org.uk/diamond-jubilee and tick the, ‘yes I’m writing a thank you letter‘ box to tell us they’ve done it. They can also share their stories with others if they wish.