Lower house of the UK Parliament
Source (Wikipedia): House of Commons of the United Kingdom

The House of Commons is the lower house of the Parliament of the United Kingdom. Like the upper house, the House of Lords, it meets in the Palace of Westminster in London, England. The House of Commons is an elected body consisting of 650 members known as members of Parliament (MPs), who are elected to represent constituencies by the first-past-the-post system and hold their seats until Parliament is dissolved.