The decision on when to hold a general election is made by the Prime Minister. For electoral purposes Britain is divided into constituencies, each of which returns one MP to the House of Commons. The British electoral system is based on the relative majority method sometimes called the 'first past the post' principle which means the candidate with more votes than any other is elected. All British citizens together with citizens of other Commonwealth countries and citizens of the Irish Republic resident in Britain may vote, provided they are aged 18 years or over and not legally barred from voting. People not entitled to vote include those serving prison sentences, peers and peeresses who are members of the House of Lords, and those kept in hospital under mental health legislation.
Voting is by secret ballot.
The elector selects just one candidate on the ballot paper and marks an 'X' by the candidate's name. Voting in elections is voluntary. On average about 75 per cent of the electorate votes. Any person aged 21 or over who is a British citizen or citizen of another Commonwealth country or the Irish Republic may stand for election to Parliament, provided they are not disqualified. People disqualified include those who are bankrupt, those sentenced to more than one year's imprisonment, members of the clergy, members of the House of Lords, and a range of public servants and officials.