Back in 1991 poll tax was superseded by the newer council tax system. The Government needed every property in the land to be put in a valuation band. Time was short, and the job was huge, so the government department responsible appointed estate agents, surveyors and other ‘experts’ to help.
Even with all the estate agents’ help, they didn’t have time to get the detailed information together, so they set about doing it quickly by pairing up and driving down countless streets, allocating each property a band with just a glance. They became known as “2nd gear bandings” or “drive-by valuations” as they mostly never even stopped their cars, never mind got out of them.
Many years passed, and still nobody came to rescue the poor valuations. So the flawed old valuation still dictates much of the United Kingdom’s banding, which is why you could be paying more than your neighbour even though you live in exactly the SAME size property.