Queen Elizabeth, whose public engagements have been limited in recent months due to mobility issues, made a surprise appearance on Tuesday at a ceremony to mark the completion of a long-awaited London train line named in her honour.
The Queen was joined by son Prince Edward, as she made a special appearance at London's Paddington Station.
Commenting on the Queen's appearance, a royal correspondent said, "As is now the new normal for the Queen's diary, the monarch's attendance was only confirmed on the day of the engagement (due to episodic mobility problems)."
He said there was no mention of it being a possibility when Buckingham Palace sent out details to media last week.