The station, a former pirate radio that now mainly broadcasts rock music, had apologised after messages falsely announcing the monarch’s death were aired.

One of the messages stated that normal programming had been suspended “as a mark of respect following the passing of His Majesty King Charles III”.

The station then played the national anthem, followed by about 16 minutes of silence before regular programming resumed.

According to Ofcom, the presenter apologised about 30 minutes after the false announcement was initially broadcast.

The regulator, which received two complaints about the incident, said the broadcast breached two of its rules due to the “very significant inaccuracy” and the delay in correcting the mistake.

One of the rules requires news reports to be accurate and impartial, while another requires broadcasters to promptly acknowledge and correct significant mistakes.

Radio Caroline explained that the incident occurred when a staff member accessed pre-recorded audio files prepared for use in the event of the King’s death while carrying out maintenance on a studio computer.

The staff member reportedly played the files “out of curiosity”, which interrupted the remote presenter’s stream and caused the recordings to be broadcast.

According to Ofcom, the staff member panicked after realising what had happened and left the premises.

The station said the remote presenter did not realise that the broadcast had been interrupted because they were not monitoring the output through an internet monitor.

The presenter also did not immediately respond to calls from colleagues who had noticed the error because they were not actively monitoring their phone.

Radio Caroline said the staff member responsible had been reprimanded and apologised, while the pre-recorded files had since been removed from the studio computer.