Blackburn with Darwen were in a group of 18 new unitary authorities which split from the local shire counties. They were the last wave of a process which began with the Local Government Act 1992 and the creation of the Isle of Wight as a unitary authority back in 1995.

The move towards unitaries was the brainchild of Michael Heseltine, the former Conservative deputy prime minister, who wanted to give cities more control over their own affairs.

It gathered pace in 1996, when the former counties of Avon, Cleveland and Humbrside were split into their constituent parts. And in 1997 and 1998 a number of large cities, towns and groups of towns (such as Leicester, Blackpool and the Medway) who had felt neglected by their county councils struck out on their own.

Although a TES analysis of school performance and social deprivation (see panel, right) puts many of these unitary authorities near the bottom of the local authority league, many have shown a sharp improvement in pupil performance since they came into being.

For example, Brighton and Hove, Southampton, Kingston-upon Hull and Portsmouth have all won a place in the Government’s list of the top 12 improved authorities since 1997.