The Home Office is not only one of the largest departments of state in the British government - it is also one of the most complicated.
Spending some £13bn a year, the Home Office is more than just a typical interior ministry because its responsibilities include huge swathes of public policy beyond just law and order.
But what exactly does it do? Its workings can be broken down into five overlapping themes:
- Core functions and goals
- Ministerial responsibilities
- Home Office management
- Public bodies
- Its relationship with other parts of Whitehall
The Home Office says its purpose is "to build a safe, just and tolerant society". At the heart of this statement is the management of three core services, or pillars: the Police in England and Wales (Scottish police are a devolved matter), crime, justice and offending, and the Immigration and Nationality Directorate.
With these key policy areas in mind, the Home Office has a strategic plan which dictates the thrust of policy for its 70,000 staff in each of their agencies, departments, sub-departments, units and teams. The goals are:
To ensure people feel more secure in their homes and lives
- To catch more offenders - and stop them offending
- To reduce drug and alcohol abuse
- To manage migration for the UK's benefit
- To engage people and communities in improving society
Top team: John Reid (Home Secretary), Liam Byrne (immigration), Tony McNulty (policing), Baroness Scotland (offenders and justice) and Permanent Secretary Sir David Normington
At the top of the tree are the ministers, appointed by the prime minister and accountable to Parliament.
The Home Office has seven ministers, headed by Home Secretary John Reid, who sits in the Cabinet. Mr Reid is responsible for all policy and its implementation within the Home Office. Ministers and senior civil servants report directly to him.
There is then one minister-of-state plus an under-secretary (the first rung on the ministerial ladder) for each of the three core services, or pillars.
Liam Byrne is minister for nationality, citizenship and immigration.
Baroness Scotland is minister for criminal justice and offender management.
Tony McNulty is minister for policing, security and community safety.
Home Office management
The most important civil servant is the Permanent Secretary, currently Sir David Normington, who answers directly to the home secretary.
Sir David heads the Home Office's "Group Executive Board" which includes the chiefs of eight policy areas, including policing, offending, immigration, criminal justice reform and internal functions such as personnel. Each of these heads have thousands of staff beneath them - but it still the job of ministers and the top civil servants to be across what they are doing.
Entirely separately to this group of eight, are five other policy chiefs who answer directly to the Permanent Secretary on key issues. These include Louise Casey (head of the government's "Respect agenda"), the Home Office's communications director, the legal chief and the director of the department's vast team of researchers, scientists and statisticians.
Public bodies and agencies
While the corporate centre of the Home Office devises policy, it's up to its public bodies and agencies to actually get things done.
The most obvious of these bodies is the police constabularies. Then there are other bodies such as the new Serious Organised Crime Agency, the UK's version of the FBI.
Two key bodies which deal with criminals, the Prison Service and Probation Service, are held together under the "National Offender Management Service".
Then there is the enormous immigration system which is itself divided into separate units such as asylum, visas, economic migration channels, enforcement and so on. This is being turned into an arms-length executive agency to try to improve its performance.
Some parts of the Home Office deal with carefully defined issues, such as the Forensic Science Service, Criminal Records Bureau and the Identity and Passport Service.
Then, entirely separate to these core areas are another two categories of public bodies.
Four watchdogs, the inspectorates of Constabulary, Prisons, Probation and the Prisons and Probation Ombudsman, are funded by the Home Office but operate independently of the Home Secretary.
Secondly, there are many non-departmental public bodies, otherwise known as quangos. These include big bodies such as the Commission for Racial Equality, the Parole Board and Sentencing Advisory Panel. But there are also much smaller bodies such as the Animal Procedures Committee, charged with looking at animal experimentation issues.
Relationship with other parts of Whitehall
The Home Office's relationship with other Whitehall departments is a crucial element of understanding what it does. Take criminal justice, for example.
The Office for Criminal Justice Reform is in fact a cross-departmental team charged with making sure there is joined-up thinking between the Home Office, Department for Constitutional Affairs (courts and law) and the Attorney General's Office, the government's chief legal advisor.
Then there are relationships with the prime minister and his own policy team. The "respect agenda" is one such Home Office priority that is closely associated with the prime minister, rather than the department.
On security issues, MI5 is answerable to the home secretary but, in reality, it also works directly with the prime minister and has complex relationships throughout Whitehall.
Sometimes, these inter-governmental relationships can be quite complicated affairs. The NHS has historically depended on foreign staff. This has historically meant there needs to be a healthy relationship between the Department of Health and the Home Office on immigration policy.