The Barbican is a Grade II listed building. (They use Roman numbers for some reason. ‘Grade II’ is simply ‘Grade 2’.)

The authorities keep a list of buildings of special architectural or historic interest. A building included in this list is colloquially called a ‘listed building.’ Listed buildings are protected against demolition; and alterations to them are severely restricted. Listed buildings come in all shapes and sizes. They include cathedrals and castles, but also milestones, village pumps and – now that the Barbican is listed – a few concrete tower blocks.

Listed buildings are classed in grades to show their relative importance. A tiny number (1.4%) are Grade I buildings. The huge majority (94.5%) are Grade II. A small number (4.1%) are better than Grade II but not quite Westminster Abbey, and these are called “Grade II*” – Grade two star. The Barbican is Grade II, but the Golden Lane Estate has one Grade II* building – Crescent House.

The Barbican Estate website www.cityoflondon.gov.uk/beo publishes details of what works in the Barbican require or don’t require listed building consent. If in doubt, consult the planning department.

It is important to understand that even the smallest internal or external change may require listed building consent – altering the skirting boards requires it, even changing the window boxes requires it. So be careful. If you break the rules, it’s actually a criminal offence. You may not be able to sell your flat, even years down the line, if you can’t prove you had the necessary permission for an alteration – or a letter saying you didn’t need permission.

The fact that a building is listed does not necessarily mean that it must be preserved intact for all time; the main purpose of listing is to ensure that care will be taken over decisions affecting its future, that any alterations respect the particular character and interest of the building, and that the case for its preservation is taken fully into account in considering the merits of any redevelopment proposals. In all cases the criterion to be considered is whether a proposed item of work will affect the building’s character in relation to its special architectural interest.