and exit to the UK at air, sea, land, and rail ports and identifies, monitors, and removes immigration offenders. The Home Secretary is a member of the full Defense and Overseas Policy ministerial committee, deputy chair of the DOP's international terrorism subcommittee, and chair of the DOP's protective security and resilience subcommittee. The Home Secretary also chairs the Civil Contingencies Committee and sits on the Intelligence Services ministerial committee. Policing in the UK is largely decentralized. The Home Office has ministerial responsibility for the police services in England and Wales. The Scottish Ministry of Justice has ministerial responsibility for policing in Scotland, while the Secretary of State for Northern Ireland sets policy for policing there. Operational control, however, of all of the police services in England, Wales, Scotland, and Northern Ireland rests with the chief constable of each force. Currently, there are 43 regional police forces in England and Wales, and 1 in Scotland; the Police Service of Northern Ireland (PSNI) is responsible for policing in Northern Ireland. In England, Wales, and Scotland, these regional police forces have primary responsibility for the investigation of terrorist offenses; the PSNI has lead responsibility for terrorist investigations related to the affairs of Northern Ireland. Each police force also has its own Special Branch, which works in partnership with the Security Service (MI5), the UK's domestic security service, to acquire intelligence on those who may be involved in terrorism. The Metropolitan Police (Scotland Yard) has responsibility for London and also has various specialist units, such as those that deal with anti-terrorism, that may be called upon to fulfill a national role. In addition to the regional forces, there are a few other British police forces that may play a role in homeland security affairs. The British Transport Police (BTP) police the railway systems of England, Wales, and Scotland; the BTP is also responsible for policing some metro and commuter systems, including the London Underground. The Department of Transport has ministerial responsibility over the BTP. The Civil Nuclear Constabulary (CNC) is an armed police force that protects civil nuclear installations and nuclear materials in the UK; it operates under the strategic direction of the Department of Trade and Industry. Although the police and security services have the primary role in domestic protection against terrorism, the armed forces may be called upon domestically in the event of a major terrorist incident requiring military units with specialized