Sarah Mullally
Sarah Mullally bangs on the door with her crosier during a ceremony to install her as the 133rd Bishop of London at St Paul's Cathedral in London on May 12, 2018.  YUI MOK/AFP/Getty Images

Sarah Mullally has been installed as the 133rd Bishop of London, making her the first female Bishop of the state, at a service held at St Paul's Cathedral on Saturday.

The 56-year-old takes over from Dr. Richard Chartres, who retired in February 2017.

Mullally is also the Church of England's third most senior cleric, after the archbishops of Canterbury and York.

During the service, she performed the tradition of knocking three times on the Cathedral's Great West door with her pastoral staff.

Mullally preached on the theme of "being subversive for Christ" during her sermon. She also talked about the challenges facing London.

"We need to speak up for the whole of London, to work to challenge the violence and the crime that have led mothers to clean their own children's blood from our pavements...Could there be a starker image or a more urgent wake-up call for all who love this city, who believe it can have an even better future?" she said, according to Agence France-Presse.

Who is Sarah Mullally?

Sarah Mullally was born in 1962 and had an illustrative career in nursing. She held a number of nursing leadership roles like in Westminster Hospital and then as director of nursing at the Chelsea and Westminster. She later became the deputy and acting chief executive officer.

She was also installed as the Bishop of London on International Nurses Day -- Florence Nightingale's birthday.

She was made a Dame Commander of the British Empire in 2005.

"It's a real privilege, and I recognize I need to use it wisely," she said about the seat in the House of Lords, which she will take later this month as the bishop of London, according to The Guardian.

She is expected to focus on three areas: London issues, health, and nursing. She also said that she will stand up for marginalized groups like women, the homeless, young people.

"I hope to give a voice to women who, for whatever reason, feel marginalized. And to ask what I can do to encourage and empower women to do the best they can,' she added, as reported by the website.

Though Mullally is the female Bishop of London, other Anglican churches across the world have been appointing female bishops for years. The United States had appointed the first female Bishop -- Barbara Clementine Harris -- in 1989.