The Duke and Duchess of Cambridge and their family have been photographed inadvertently breaking the rule of six by mixing with fellow Royals at Sandringham.
Prince William and Kate, visiting with their children George, Charlotte and Louis, were seen walking in tandem with Prince Edward and his own family of four on Sunday evening.
They met as they enjoyed Luminate, a festive attraction currently being held at the Queen's Norfolk residence, which sees visitors walk through surrounding woodland.
While the encounter saw the party total a group of nine, a royal source indicated there had been no prior intention for the two families to meet.
They were, however, pictured walking together along the illuminated trail, albeit adhering to social distancing.
The source said: "The two families were given separate consecutive slots to visit the trail just before it opened to the general public. They arrived, and departed in their own family groups.
"As anyone with young children will know, there were moments on the 90-minute walk where it was difficult to keep the two family groups apart particularly at bottlenecks on the trail."
Current rules aimed at limiting the spread of coronavirus prevent groups of more than six people from meeting outside if they are not from the same household or support bubble.
Having mixed in Norfolk, the princes and their families were in a Tier 2 area - although the rule of six applies even at the lowest alert level, Tier 1.
Police are permitted to disperse gatherings of groups larger than six and issue fines of £200, potentially rising to £6,400 with further offences.
For the past 10 days or so, Prince William and family have been staying at Anmer Hall, their countryside retreat on the Sandringham Estate, where they also rode out the first nationwide lockdown.
They journeyed to Anmer before the introduction of Tier 3 and Tier 4 rules prohibited non-essential travel from London, where they live at Kensington Palace.
Prince Edward, William's uncle, was visiting Luminate with his wife, Sophie, and their children Lady Louise Windsor and James Viscount Severn.
They had travelled to Norfolk from their home at Bagshot Park in Surrey.
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