Security

The Gentleman Usher of the Black Rod oversees security for the House of Lords, whilst the Serjeant-at-Arms does the same for the House of Commons. These officers, however, have primarily ceremonial roles outside the actual chambers of their respective Houses. Security is the responsibility of the Palace of Westminster Division of the Metropolitan Police, the police force for the Greater London area.

Probably the most famous attempt to breach the security of the Palace of Westminster occurred with the Gunpowder Plot of 1605. The plot was an attempt by Roman Catholic extremists to cause an explosion in the Palace of Westminster during the State Opening of Parliament, thereby killing the Protestant King James I, his family, and most of the aristocracy. The plot was discovered, however, when a Roman Catholic nobleman, William Parker, 4th Baron Monteagle, received an anonymous letter warning him not to attend the State Opening. The authorities conducted a search of the Palace, discovered the gunpowder, as well as one of the conspirators, Guy Fawkes. The conspirators were later tried for high treason in Westminster Hall, and were hanged, drawn, and quartered. Since 1605, the Yeomen of the Guard have conducted a ceremonial search of the Palace's cellars prior to each State Opening of Parliament.

The previous Palace of Westminster was also the site of a prime ministerial assassination in 1812. Whilst in the lobby of the House of Commons, on his way to a parliamentary inquiry, Spencer Perceval was shot and killed by John Bellingham. Perceval remains the only British Prime Minister to have been assassinated.
On the 17 June 1974 a 20 pound (9 kg) bomb planted by the Provisional IRA exploded in Westminster Hall. In 1979 Airey Neave, a prominent Conservative politician, was killed by a car bomb as he drove out of the Palace's new car park. Both the Irish National Liberation Army and the Provisional IRA claimed responsibility for the murder; security forces believe the former were actually responsible. With rising concern about the possibility of a truck full of explosives being driven into the building (despite the effective cessation by that time of Northern Irish terrorism), a series of concrete blocks was placed in the roadway in 2003.

Tony Blair being hit by a flour bomb. The Palace has also been the site of a number of acts of politically motivated "direct action". In 1970, for example, some individuals threw a canister of tear gas into the Chamber of the House of Commons to protest against conditions in Northern Ireland, and in the same cause in 1978 manure was thrown by, among others, the daughter of Dom Mintoff. Concern about such attacks and a possible chemical or biological attack led to the construction of a glass screen across the Strangers' Gallery in early 2004.

The new barrier did not cover the front three rows, which are termed the "Distinguished Strangers' Gallery" and in May of that year protesters from Fathers 4 Justice attacked Prime Minister Tony Blair with flour bombs from this part. In September, five protesters opposed to the proposed ban on fox hunting disrupted the proceedings of the House of Commons by running into the Chamber. Despite such disruptions, members of the public continue to have access to the Galleries.

Culture and tourism

The exterior of the Palace of Westminster—especially the Clock Tower—is one of the most visited tourist attractions in London. The United Nations Educational, Scientific and Cultural Organization (UNESCO) classifies the Palace of Westminster as a World Heritage Site. It is also a Grade I listed building. There is no casual access to the interior, but it may be seen in a number of ways:

•Viewing debates from the public galleries of the House of Commons or the House of Lords: UK residents may obtain tickets in advance from their MP. It is also possible for both UK residents and overseas visitors to queue for admission on the day, but capacity is limited and there is no guarantee of admission. Only a very small part of the Palace's interior may be seen. Either House may exclude "strangers" if it desires to sit in private.

•Tours during Parliamentary sessions: UK residents may apply to their MP or a peer for a place on a guided tour of Parliament while it is in session. British educational institutions may also arrange a tour through their MP. The system for issuing overseas visitors with permits to tour the Palace while Parliament is in session has been suspended temporarily.

•Summer opening: tours are available during a two-month period during the summer when Parliament is not sitting. These tours are open to both UK residents and overseas visitors. Advance bookings are recommended.

Since 1 August 2005, it has been illegal to hold a protest within half a mile (1 km) of the Palace without the prior permission of the Metropolitan Police.