The Duke and Duchess of Cambridge and their children have been pictured at an outdoor event with the Earl of Wessex and his family, inadvertently breaching of the Rule of Six.
William and Kate took their family to Luminate, a night-time woodland walk on the Queen's Sandringham estate, on Sunday and were photographed at one point walking at a distance with Edward and Sophie and their two children.
Norfolk is in Tier 2 and, under restrictions, only up to six people can meet up outside – known as the Rule of Six.
In one image published in the Daily Mail, William leads the group with his youngest son, Prince Louis, on his shoulders. Prince George and Princess Charlotte are close by, with Kate behind them and Sophie and her son, Viscount Severn, alongside.
Lady Louise follows behind her mother, the countess, with the earl at the back, making nine people in total.
The event, which is open to the public, is billed on the estate's website as a "spectacular, illuminated trail, full of wonder and intrigue, to delight and enthral your senses".
The Cambridges and the Wessexes arrived separately but were seen "mingling" together several times, according to a member of the public who took photographs on their smartphone.
The Earl and Countess of Wessex live in Bagshot Park in Surrey, which was put into Tier 4 on Sunday, with residents of this tier asked not to leave home unless they have a reasonable excuse.
But it is understood the couple and their family had left their home when it was still in Tier 2.
William and Kate live close to Sandringham in their country home, Anmer Hall, and it is thought they moved to the residence from their London home at Kensington Palace after the school holidays began.
A source at Sandringham 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."