The current Bishop of Crediton and future Bishop of London spent most of her career – 35 years – working in the National Health Service, having initially trained as a nurse.

She was appointed as the youngest Chief Nursing Officer for England in 1999, with responsibility for more than 400,000 nurses and midwives. In 2015 she was appointed Dame Commander of the Order of the British Empire in recognition of her services to nursing and midwifery.

From 2005 to 2013 she was vice-chair and non executive director at the Royal Marsden NHS Foundation Trust from 2005 to 2013 and is currently a non executive director at Salisbury NHS Foundation Trust.

Mullally trained part-time for Anglican ministry, becoming a deacon in 2001 and priest in 2002. She was an assistant curate at St Saviour's in Battersea Fields from 2001. She completed an MA in Pastoral Theology at Heythrop College in 2006 and was appointed as Rector to the Sutton Team Ministry the same year. She was consecrated as the Church of England's fourth woman bishop in 2015.

She is married with two children and is an amateur potter.

In an interview with the Church Times in 2009 she said she had had a Christian faith since the age of 16. She also revealed she has dyslexia, saying she hated reading the genealogies in Scripture – 'the words run off the paper like paint'.

Mullally is a prolific tweeter and in August she was identified by Premier as the most active bishop on the site. She is not identified with the evangelical wing of the Church, but said one of her reasons was evangelism: 'Twitter is a way of communicating the good news of the gospel to a whole series of people who may not encounter church.' She blogs once or twice a month but avoids controversial topics. Mullally was one of the 10 bishops appointed to the 'Bishops' reflection group on sexuality' tasked with taking forward the Church of England's 'discernment process' on same-sex relationships, but is not a high-profile campaigner on either side of the debate. Whether she will be able to satisfy conservative churches like St Helen's Bishopsgate of her orthodoxy is a key question for her ability to hold a diverse diocese together, and one that will have been at the forefront of the selection panel's concerns.

When she was appointed to Crediton she told the Daily Telegraph it was important not to obsess about empty pews. 'I think that the Church does need to take seriously the change in the Church's membership and that is important but part of that is also to recognise that there are really good examples where the church engages with individuals that isn't around the pews,' she said.