able to return members, but six small counties were arranged in an alternating scheme whereby only three would return a member at each election, giving a total of 45 MPs). These 558 were again increased to 658 by the Act of Union 1800, with the addition of MPs for Ireland. Over the next 85 years the number of seats varied only slightly, as constituencies were disenfranchised for corruption and the seats were re-allocated some time later (see the lists below for details). The major redistributions of constituencies following the Reform Act 1832 and Reform Act 1867 both created a new House (elected in 1832 and 1868 respectively) with exactly 658 seats. The number of MPs had dropped to 648 by the dissolution before the General Election of 1885. With the Redistribution of Seats Act 1885, introduced in the wake of the Reform Act of 1884, the size of the House was increased to 670 and remained unchanged until the Representation of the People Act at the end of the First World War. The period between 1918 and 1922 saw the most MPs in the history of Parliament with 707 seats. From 1922 the number of seats has fluctuated between 615 and 659. Unlike the position in many countries, such as the United States and Australia, seats are not allocated to different parts of the United Kingdom by a strict mathematical formula. The total number of seats result from the decisions of the four national Boundary Commissions, each applying the rules from time to time provided for by Parliament. Up to the fifth general review of parliamentary boundaries, the usual effect of the interaction of the rules applied by the four national boundary commissions was to over-represent the non-English parts of the United Kingdom compared to England. The number of seats in each redistribution also tended to rise (although Northern Ireland was under represented between 1922 and 1983 as for most of that time it had a devolved government and from the 2005 redistribution Scotland used the same quota of average number of electors per constituency as England as it now has devolved institutions). The Parliamentary Voting System and Constituencies Act 2011, amended the rules. For the first time the total number of members of parliament was to be fixed (at 600) and a mathematical formula was prescribed for apportioning seats between the four parts of the United Kingdom. As a