Cressida Dick arriving at New Scotland Yard to formally takes up the role of commissioner
But after Sir Bernard Hogan-Howe's retirement was announced, she quickly emerged as the frontrunner in the race to succeed him as Metropolitan Police commissioner.
Today the 56-year-old becomes Britain's most senior and prominent police officer, in charge of an organisation with more than 43,000 officers and staff and a £3 billion budget.
She is the first female commissioner in the 188-year history of the country's largest police force.
Commissioner Dick had spent more than 30 years working in policing prior to her departure from the Met for a low-profile role at the Foreign Office in 2015.
The daughter of two academics, she was born, brought up and educated in Oxford.
After graduating from Oxford University's Balliol College with a degree in agriculture and forest sciences, she worked briefly in accountancy before joining the Met in 1983.
Commissioner Dick spent more than 30 years working in policing
Commissioner Dick served as a WPC, sergeant and inspector in central south-west and south-east London.
In 1995 she transferred to Thames Valley Police as a superintendent and spent three years as area commander at Oxford.
She took a career break to study for a Master's degree in criminology at Cambridge University, before rejoining the Met as a commander in 2001.
During her second stint at the force, Commissioner Dick took on command roles in the police response to the 9/11 attacks and the tsunami in December 2004.
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She was thrust into the public eye in 2005 after she was in charge of the disastrous operation that led to the fatal shooting of Brazilian Jean Charles de Menezes, who was wrongly identified as a potential suicide bomber.
A jury later cleared Commissioner Dick of any blame in his death.
In 2007 she was promoted to deputy assistant commissioner and became the Met's first female assistant commissioner two years later.
She was the national lead for counter-terrorism for three years, and led the security operations for the Queen's Diamond Jubilee and 2012 Olympics.
Commissioner Dick was the national lead for counter-terrorism for three years
Her work at the Met also included leading the re-investigation into the murder of Stephen Lawrence and the police response to the killing of Lee Rigby.
Commissioner Dick left Scotland Yard in January 2015 to join the Foreign Office as a director general.
She was awarded the Queen's Police Medal for services to policing in 2010 and a CBE in 2015.
Commissioner Dick left Scotland Yard in January 2015 to join the Foreign Office
In 2013, Commissioner Dick was named among the 100 most powerful women in the UK by Radio 4's Woman's Hour.
The new commissioner said her appointment was "beyond my wildest dreams" when it was announced in February.
Last week it emerged she had chosen to take an annual salary of £230,000 – which is £40,000 less than the pay package she was offered.