The first past the post electoral system depends upon single member constituencies with approximately the same number of electors in each.
How to explain then, to take but one example, that in 2010 the 110,924 electors in the Isle of Wight elected a single MP as did the 21,837 electors in Na h-Eileanan an Iar (formerly the Western Isles)?
Source: Michael Pinto-Duschinsky, Standpoint magazine, April 2015