What is a Cathedral?
A cathedral is the name given to the main church for the area administered by a bishop called a Diocese. It is named after "cathedra" or seat of the bishop.
After founding the Church of England in 1534 Henry VIII created 6 cathedral towns in the 1540's and gave them all city status by letters patent. This created the association between having a cathedral and city status. The other towns with cathedrals at the time also became to be considered cities since "time immemorial". There were no Church of England cathedrals created between 1542 and 1836.
Only towns with Anglican cathedrals were recognised as "cathedral cities". In Scotland the Scottish Episcopal Church is part of the Anglican Communion and the cathedrals are referred to as Episcopal Cathedrals. In Wales the sister church is called the Church in Wales and in Northern Ireland the sister church is the Church of Ireland. See Table 1 for a list of UK towns with Anglican or Episcopal cathedrals and see Table 5 for all UK towns with Catholic cathedrals.
Does a town need an Anglican cathedral to become a city?
NO. There are 18 cities without an Anglican (or Scottish Episcopal) cathedral and 13 towns which have an Anglican or (Scottish Episcopal) cathedral but do not have city status.
The government in the 1880's tried to maintain the link between city status and an Anglican cathedral after new cathedrals were founded in Liverpool, Wakefield and Newcastle and all three towns were given city status soon after. This became increasingly more difficult to do when the small village of Southwell got a Cathedral in 1884 and big cities like Birmingham and Belfast without cathedrals were still waiting for city status.
In the end government finally broke the link between cathedrals and cities when they decided Belfast and Birmingham could become cities without cathedrals and Southwell would remain a town. Both Birmingham and Belfast eventually did get Anglican cathedrals some years after gaining city status.