The latest twist in the saga of a Hampstead landlord who refuses to pay a controversial levy saw him bring a top barrister to his court hearing.

The lawyer then called for a full liability order hearing into whether or not he Jimmy McGrath will be forced to pay the Hampstead Business Improvement District (BID) fee.

Jimmy McGrath, 79, surprised the court by arriving flanked by Robert Griffiths QC – a lawyer more used to representing the likes of the French embassy – who went on to tell the magistrates the BID was “unconstitutional”.

Jimmy – who runs the King William IV pub in Hampstead High Street – owes more than £900 after refusing to pay the levy, which was brought in after a 2016 referendum of business in Hampstead.

Camden Council are not directly involved in the BID – which is run by a private limited company – but as the local billing authority it enforces payment of the levy.

In court, Robert Griffiths QC said: “This case raises what you could call a cause celebre in north London, but it may be more than that.

“The BID is unconstitutional and amounts to a destruction and abuse of process and the common law contract.”

He argued the delegation of local authority powers to a private committee was “not what localism should mean”.

Mr Griffiths also told magistrates necessary paperwork had not been served on his client,

He said: “There’s a need to serve a demand notice. In that notice it must be set out what has been spent in the previous financial year, and what is due to be spent in the next one. If that has been done we have not seen it.“

For Camden Council, Charles Quick confirmed Camden would disclose all enforcement correspondence ahead of the next hearing but said: “I am not sure as to the scope of the court to consider some of the issues raised.”

The case has been adjourned until December 13 when the court is expected to set out directions for a full hearing on the issue, which would take place in early 2019.

Jimmy told this newspaper: “When I said I’d bring a QC along, it was a bit of an idle threat really, but here we are.”

Last month the BID’s chief executive Caroline Goldsack revealed she was to step down in December. A replacement has yet to be named. Hampstead Village BID Ltd has been approached for comment.