Mrs May, member of Parliament for Maidenhead since 1997, spent the full term of the last coalition government at the department.
She was greeted by the familiar face of the Permanent Secretary Mark Sedwill as she returned to the Westminster offices.
She said:
We’ve achieved a lot over the last 5 years at the Home Office – all the police reform that has been done, Police and Crime Commissioners, setting up the College of Policing, the National Crime Agency, the work that has been done on modern slavery, for example, and of course on immigration. But there is more to do and I’m keen to get on and do it.