Lady Jane Williams passed away peacefully on Saturday morning, Lambeth Palace said.
The Most Rev Justin Welby said she led a “remarkable” life, working for Winston Churchill and Nobel Prize winner Professor Sir Ernst Chain.
Mr Welby said he will treasure many memories of her which are “full of grace, laughter and joy.”
We are profoundly grateful to God for the gift she has been to us all – for all we received from her, and all she has meant to us
He added: “It’s with profound sadness that I mourn the loss of my mother. I loved her very deeply and it has been a privilege to be her son.
“I am the person I am in part because of her love, example and encouragement.
“Our whole family share in the loss of a mother, grandmother and great-grandmother.
“We are profoundly grateful to God for the gift she has been to us all – for all we received from her, and all she has meant to us.
“The grief we feel is a measure of the love we have shared.
“We will treasure the many memories we have of her: memories full of grace, laughter and joy.
“Towards the end of her life she showed great courage, faith and hope. She knew she would soon be with God.
“That was a source of strength for her, and for all of us, and her death was peaceful and full of hope.
“I know that many people will be praying for me and my family at this time and we are deeply grateful.”
Born in India in 1929, Lady Williams spent much of the Second World War living with her maternal uncle, Rab Butler, who was Education Secretary in the wartime cabinet.
Her first job in 1949 was working for Winston Churchill, whom she carried on working for until 1955.
She was one of the last of his personal staff and often lectured and spoke about the wartime leader later in life.
She also worked for Nobel Prize winner Professor Chain, best known for his work on penicillin, at Imperial College London.
The archbishop said he and his family were “very kind” to her.
Later in life she worked as a probation officer, for the Parole Board and as a prison visitor.
She married Lord Williams of Elvel in 1977 and they spent more than 40 “happy” years together until he died in 2019.
The archbishop said she helped “countless others to know freedom from addiction” after recovering from alcoholism.
He added: “My mother lived a full human life, with all its ups and downs.
“Her story is one of redemption – which she found through faith in Jesus Christ, and loving service to others.
“Each step in her journey towards greater fullness of life brought me such joy.”
