Although the concept of ‘one person, one vote’ seems axiomatic these days, that hasn’t always been the case. In the UK, plural voting was a legitimate practice for many centuries.
The right to vote in the UK was traditionally governed by a hodgepodge of requirements. There were two types of constituency: county constituencies and borough constituencies. For county constituencies, property ownership was key (from the 15th century onward, the qualification was holding a freehold worth 40 shillings per year). For borough constituencies, the qualifications were more varied, but property ownership could still confer voting rights in certain cases.
If a person owned qualifying property in multiple constituencies, they had a vote in each one. There was no limit on the number of votes one could obtain that way. Speaking in 1892, George Shaw-Lefevre MP noted some particularly extreme examples:
I think it was Sir Robert Fowler, a late Member of this House, who used to boast that he had no fewer than thirteen votes in different constituencies, and that he was able at one General Election to record them all. Then there is the well-known case of the Oxford tutor—a man who had eighteen different qualifications, and, at the Election of 1874, voted in respect of these different qualifications eighteen times. But this case pales before one I heard of recently. A clergyman of the Church of England, who has a hobby for acquiring qualifications in different constituencies, has been able to obtain fifty votes in different places, and I was informed that at a certain General Election he contrived to vote in no fewer than forty different places.
A person might also enjoy an additional vote if they were a graduate of a university. Initially, Oxford and Cambridge were the only university constituencies, but they were joined by others over the course of the 19th and 20th centuries. By the time these constituencies were abolished in 1950, universities were sending 12 MPs to the Commons.
Despite successive efforts to regularize and expand the franchise over the course of the 19th century, plural voting persisted. While many in the Liberal party opposed the practice, Conservatives tended to support it as a time-honored right (Tories also pointed out that some of Britain’s best statesmen came from university constituencies). There were several attempts to abolish the practice through Private Members’ Bill, but none made it onto the statute book. Eventually, the Representation of the People Act 1918 limited plural voting in General Elections to two votes: one from residency and one from another qualification. The practice was finally abolished for parliamentary elections by the Representation of the People Act 1948, which also did away with university constituencies.
Plural voting remained a possibility in local elections until the Representation of the People Act 1969 abolished outside of the City of London. To this day, a form of plural voting is still possible in the City since businesses and other organizations are allowed to nominate a certain number of voters based on their workforce. These voters aren’t required to be residents of the City, so if they are eligible to vote elsewhere, they can vote in both elections.
 Charles Seymour, Electoral Reform in England and Wales: The Development and Operation of the Parliamentary Franchise, 1832-1885 (New Haven: Yale University Press, 1915), 11.
 See Seymour, 25-27 for an overview of the different borough requirements.
 HC Hansard, 18 May 1892, cols. 1184-85.
 The Irish Senate still has university constituencies.
 It took effect with the 1950 General Election.
 The City of London is distinct from Greater London.
 The justification for this is that the city’s workforce far outnumbers its resident population by a considerable amount. Although nominated voters represent businesses/organizations, elections are done by secret ballot, so nominated voters still get to make their own decision at the ballot box.