The BBC breached broadcasting guidelines by failing to warn viewers about a clip of Prince William and Kate Middleton's engagement announcement containing flashing images, watchdog Ofcom has ruled.
The clip was used by BBC News At Ten on November 23, for the story stating that the couple would marry at Westminster Abbey on April 29.
The flashing images were caused by flash photography of the couple and of the engagement ring at the photocall.
The story was introduced by News At Ten presenter Huw Edwards, who handed over to royal correspondent June Kelly, live at Westminster Abbey.
Kelly then introduced a pre-recorded news package for the story, which contained the clip.
Certain types of flashing images can trigger seizures in viewers who are susceptible to photosensitive epilepsy.
The BBC apologised for the "oversight" and said its news teams had since been reminded of the importance of giving sufficient warnings.
It said a warning was given in the earlier six o'clock news bulletin.
It added that the reporter on location should have been instructed to include a warning in her remarks but that this did not happen.
Broadcasting watchdog Ofcom found that 13 seconds of flashing exceeded intensity limits set out in its guidance.
It concluded that the BBC had breached broadcasting guidelines.
It said: "We noted that the BBC had taken appropriate measures to check the item, and had identified it as being problematic in advance of its transmission.
"The BBC had apologised for not including an appropriate warning on this occasion.
"Ofcom acknowledges that the omission of a warning was as a result of human error on this occasion, and that the BBC news teams have taken additional compliance measures in response to this.
"However, the omission of a warning in circumstances where the BBC was aware the material was problematic is a matter of concern to Ofcom, and we do not expect a recurrence."