The Archbishop of Canterbury has said he has "never got over" the loss of his eldest daughter in a candid message to bereaved families.

Justin Welby's daughter Johanna was killed in car crash 30 years ago when she was less than a year old. He spoke at a carol service held by Child Bereavement UK on December 10, a charity which supports families coming to terms with a loss.

"We never 'get over it' –  that's such an atrocious expression  – but we do begin to rebuild," said Welby in the service held at HTB, the charismatic church in central London attended by the Welbys before he was ordained.

"If we're wise, and if we have wise friends who love us... eventually we begin to look up a bit."

Welby spoke honestly about "tough words, bitter words of anger with God" and the struggle he and his wife Caroline experienced with unanswered questions.

Christmas, he said, was a particularly difficult time.

"You hear that reading about the shepherds and their joy and you think, 'Fine for them... doesn't feel much like that to me.'"

But Welby said that ultimately, he found comfort in the "great puzzle" of the Christmas message.

"There is one child in the whole of human history who died, whose father could have done something and didn't. Who could with a mere exercise of will have changed the world so it didn't happen.

"His beloved child, whom he sent, whom the angels announced, whom he sent to live this risky life, and who died unjustly some 30 years later, out of time, unfairly."

This story of Christ's birth was a source of "hope and healing" for his family, said Welby.

"We find a source of purpose, a source of going on, that is so boundlessly deep, so extraordinarily puzzling sometimes, but so wonderfully embracing, that in the dark moments and the light moments we are held and comforted and carried."

Welby explained that his daughter's birthday and anniversary were particulary difficult. "There's always that reality, and yet there's now that hope."

"I pray for you and for all of us here," he concluded. "For that hope that heals and strengthens and draws us forward, because that child who was born and risked and died and rose again, and offers life to us and to all we love. Amen."