The Church of England will today take the historic step of voting on whether to give final approval to legislation introducing the first female bishops.
The General Synod, the Church's national assembly, will take a series of votes after a debate on whether to allow the legislation to clear its final hurdle before going to Parliament for approval.
The vote is billed as the most significant step in 20 years taken by the General Synod, a 470-strong body made up of bishops, clergy and laity, since it first backed the introduction of women priests.
If given approval later today, the legislation will go to the Houses of Parliament before receiving Royal Assent, paving the way for the first women bishops in 2014.
A vote in favour of approval would usher in not only women bishops but the prospect of future female Archbishops of Canterbury or York, the two most senior posts in the Church of England.
But the legislation needs a two-thirds majority in all three houses of the General Synod - bishops, clergy and laity - in order to gain final approval.
Commentators have said they believe the legislation will clear the houses of bishops and clergy with the necessary majority but the vote amongst lay members of the General Synod is thought to be close.
The first vote will be on whether to give final approval to the legislation with a second vote taken on a draft amending canon, a legal mechanism that will enable the legislation to become law.
A third vote will be taken on whether to back a petition for Royal Assent.
The vote comes after years of torturous negotiations on how best to introduce women bishops within the Church of England amid opposition from traditionalists including some Anglo-Catholics and conservative evangelicals.
Under the legislation, a woman bishop would delegate to a stand-in male bishop to minister to parishes which rejected her authority, using a code of practice for guidance.
The legislation has been backed by 42 out of the 44 Church of England dioceses.
But traditionalists have attacked the arrangements in the legislation as inadequate, while some pro-women campaigners have complained that the concessions have been too generous to objectors.
Currently 944 out of 12,792 parishes in the Church of England refuse to have a woman vicar.
A defeat for the legislation would be seen as a serious blow to Dr Rowan Williams, the outgoing Archbishop of Canterbury, who has staked his authority on a Yes vote in a campaign launched last month.
Dr Williams has warned that a failure to approve women bishops could be embarrassing for the Church and lead to "a period of continued and perhaps intensified internal conflict".
The incoming Archbishop of Canterbury, the Rt Rev Justin Welby, Bishop of Durham, has also urged the General Synod to vote for the legislation, saying that he is "deeply committed" to the ordination of women to the episcopate.
Yesterday members of the General Synod were asked to show "grace" to one another whatever the outcome of the debate and the vote.
The Ven Julian Henderson, Archdeacon of Dorking, said there would be "anxiety and emotion" as the General Synod debates and votes on the issue.