The Church of England's most senior woman bishop will be consecrated today in Canterbury, Kent.
The Archbishop of Canterbury, the Most Rev Justin Welby, will lead the ordination and consecration of the Ven Rachel Treweek who becomes Bishop of Gloucester.
The Rev Canon Dame Sarah Mullally, 53, a former government chief nursing officer, will also be consecrated as the Bishop of Crediton in the Diocese of Exeter in Devon.
In a fitting move, the 22-strong Canterbury Cathedral Girls' Choir - which only formed at the Kent cathedral last year - will lead the singing at the ceremony.
Former speech and language therapist Ms Treweek, who was Archdeacon of Hackney, officially becomes the Church's first female diocesan bishop.
It is understood the 52-year-old, who describes herself in her Twitter profile as "more vulnerable than venerable", will become the first woman bishop to enter the House of Lords.
Her appointment, which comes after the Right Rev Michael Perham retired in November, means she is the first woman to run a diocese and is one rank below archbishop.
She said she was "excited and full of anticipation and joy for what lies ahead" as she begins her ministry as Bishop of Gloucester.
"I am looking forward to encouraging Christians to speak out with confidence about their faith and the good news that the Gospel brings," she said.
Ms Treweek and Dame Sarah are the third and fourth female bishops to be appointed in the Church of England respectively.
Dame Sarah, a married mother-of-two, spoke last month of how she will miss her old job as Salisbury Cathedral's canon treasurer.
She said: "It has been a privilege and great joy to have been part of the cathedral community and I will miss some wonderful colleagues and friends.
"My time here has equipped me well for my ministry that is ahead in Devon and I will take much with me into my new role."
Dame Sarah was appointed as the government's chief nursing officer for England in 1999 - becoming the youngest person to hold that role.