On Monday, the feast of Epiphany in the Christian calendar, Mr Welby will attend two services at Lambeth Palace, a Eucharist at lunchtime and Evensong later in the day.
Though his office has not disclosed who will join him at these services, it is expected that he will lay down his crozier at the evening event then formally end his time as archbishop at midnight.
Mr Welby resigned over the Church’s handling of the sadistic abuser, John Smyth, who a recently published report said perpetrated brutal sexual, physical and mental abuse against more than 120 boys and young men since the late 1970s.
The report said Mr Welby had “personal and moral responsibility” and that he “could and should have done more” in the case.
After initially resisting calls to step down, he resigned on 12 November saying he did so “in sorrow with all victims and survivors of abuse”.
But in early December, abuse victims reacted with “disgust” at a short farewell speech Mr Welby gave at the House of Lords, in which he made jokes. Mr Welby apologised the following day.
Mr Welby did not give a Christmas Day sermon at Canterbury Cathedral and did not broadcast a New Year’s Day message, as he usually would through the .
Lambeth Palace said he would not be giving any interviews before leaving his role, which he is doing on Monday on his 69th birthday. He steps down exactly a year earlier than expected.
From midnight on Monday, some of his duties in London will be carried out by the Bishop of London Sarah Mullally and those in his Canterbury diocese by the Bishop of Dover Rose Hudson-Wilkin.
The bulk of his responsibilities will be carried out by Mr Cottrell, who has himself faced calls to step down over his handling of an abuse case.
Last month, a investigation revealed that in 2010, days after he became Bishop of Chelmsford, Mr Cottrell was told about multiple historical sex abuse allegations against a priest in his charge, David Tudor.
He was also told that the Church and local council had banned Tudor from being left alone with children.
Mr Cottrell said in a statement: “The situation with David Tudor was an awful situation to live with and to manage.”
“I want victims and survivors to know that everything was done to understand, assess and manage the risk,” it continued.
But under Mr Cottrell, Tudor twice had his contract in the senior post of area dean renewed and in 2015 was made honorary canon of Chelmsford Cathedral.
Tudor was only suspended in 2019 when a new police investigation was launched. Archbishop Cottrell says he acted as soon as he was legally able to.
Although he is taking on the duties of Mr Welby, Mr Cottrell will continue to be based at Bishopthorpe Palace in North Yorkshire. He is expected to be de facto leader of the Church of England until at least the summer.
