Prince George and Princess Charlotte enjoy a play date with Roger Federer's kids

Prince George and Princess Charlotte enjoyed a very special play date at Kensington Palace over the weekend, as tennis champ Roger Federer and his wife Mirka dropped in with their four children for a visit.

Federer, who has two sets of twins with his wife Mirka, lives in Switzerland, but is over in the UK with his whole family at the moment while he competes in the ATP finals.

The multiple grand-slam winning tennis star and his wife are good friends of the Cambridge's, securing sought-after invites to both the royal wedding in 2011, and Pippa Middleton's nuptials this summer.

The couple were spotted over the weekend leaving their hotel in London and making a short trip around the corner to visit their friends Kate and Prince William, with their four children in tow for a play date with the young royals.

Roger and Mirka have two sets of twins, daughters Myla Rose and Charlene Riva, who are eight, and sons Leo and Lennart, who are three – perfect playmates for four-year-old Prince George.

The family didn't arrive at Kensington Palace empty handed either. Mum Mirka was spotted carrying two neatly wrapped gifts in her arms as they arrived for their visit – thought to be two presents for the royal children – one each for George and Charlotte.

As well as a much-needed catch up for the adults, the children seemed to have enjoyed time colouring together, as one of the Federer's daughters Myla was spotted carrying a drawing with her name on it as the family left the palace a couple of hours later.

Their play date with the Federer family is not Prince George and Princess Charlotte's first brush with celebrity tots. Last year Hollywood actor Ben Affleck, who is currently playing the role of Batman, revealed that his son had a surprise royal play date with Prince George after a trip to an indoor play centre in London.

'I was the very last person to realise that Prince George and Princess Charlotte were in there playing with my kid' Ben joked in an appearance on The Graham Norton show.