Four people - including the attacker have now died, and 40 are injured after yesterday's terror attack in London.
Archbishiop Of Canterbury Quits
Rowan Williams is to step down after 10 years as Archbishop of Canterbury.
The 61 year old, who says it has been "enormous privilege" to hold the post, will leave at the end of December to take up a new role as Master of Magdalene College, Cambridge.
Lambeth Palace said the Queen, as Supreme Governor of the Church of England, has been informed.
Dr Williams was confirmed as 104th Archbishop of Canterbury and spiritual leader of the 77 million-strong Anglican Communion in December 2002. Prior to that, he was Archbishop of Wales, having been consecrated bishop of Monmouth in 1991.
Explaining his reasons for leaving, Dr Williams said: "At the end of this year I will have been 10 years in post as Archbishop and just over 20 years as a bishop - that is part of it, feeling that after 10 years it is proper to pray and reflect and review your options.''
Dr Williams said: "I think that it is a job of immense demands and I would hope that my successor has the constitution of an ox and the skin of a rhinoceros, really.
"But he will, I think, have to look with positive, hopeful eyes on a Church which, for all its problems, is still for so many people, a place to which they resort in times of need and crisis, a place to which they look for inspiration.
"I think the Church of England is a great treasure. ``I wish my successor well in the stewardship of it.''
Dr Williams will continue to carry out all the duties and responsibilities of the Archbishop of Canterbury, both for the Church of England and the Anglican Communion, until the end of the year, Lambeth Palace said.
The Crown Nominations Commission (CNC) will consider `"in due course'' the selection of a successor.
Site in Kent earmarked for development
The inquest into the deaths of three people, found at cliffs in Dover, is due to start.
An Ashford woman who stole around £100,000 from the company she worked for has been sent to prison.
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