JD Wetherspoon has been fined more than £3,000 by magistrates for not having a registered designated premises supervisor (DPS) at one of its North London pubs.
The Moon and Sixpence in Hatch End, Harrow, was fined £3,300 plus £3,800 in costs following a Harrow Council prosecution for selling alcohol without a DPS for more than a month.
Wetherspoon blamed an administration error when the last manager left the pub and was not replaced.
The breach was exposed when police following up an incident at the pub asked to speak to the licensee, and upon realising there wasn't one, referred the case to the council.
"It's essential that people with the right training and experience are in place to run licensed premises, and fulfil their duty of care to both customers and the wider community," said councillor Phillip O'Dell.
"That's why we take any breach of our strict licensing laws very seriously in Harrow and the council will not hesitate to prosecute."
A Wetherspoon spokesman said: "This was a regrettable administration error and as such Wetherspoon pleaded guilty in order to save the courts time.
"It was noted in court that there were no issues with the running of the pub during the period."