It's easy to make mistakes in town planning, which is a complicated and difficult business these days.

Brighton and Hove Council certainly made one in Marlborough Mews when it advised Derek Edmonds he did not need permission for an extension.

But now officials have realised they were in error, efforts should be made to put things right immediately.

Understandably Mr Edmonds went ahead with the extension but it is clearly causing problems for neighbours.

Now the council should issue an enforcement notice telling him work must be stopped because the scheme does need permission after all.

The council may be nervous about being sued by Mr Edmonds, who is a wealthy man. But it should be bold all the same.

Apart from anything else, if it procrastinates it may still end up being sued, this time by one of the neighbours.

Stopping the work now would enable all parties to get together and see if they can come to some sort of compromise.

The longer the council allows the development to continue, the more likely the whole affair is likely to end in a nasty mess.