Roger Federer and his two sets of twins drop in on the Cambridges at Kensington Palace ahead of tennis ace's clash with rval Marin Cilic (Details, pics)

Roger Federer and his young family had a brush with royalty when they stopped by at Kensington Palace to visit their friends Duke and Duchess of Cambridge.

The Swiss tennis ace, who is in London this week for the ATP Finals, was joined by wife Mirka and their two sets of adorable twins on Wednesday night.

The family were spotted leaving their hotel on Wednesday afternoon before making the short drive to Kate and William's home where they stayed for around two hours.

The Cambridges have recently swapped Anmer Hall in Norfolk for Kensington Palace as their official residence as they prepare to take on more royal duties.

They are close friends of the Federers, who were guests at both Kate and younger sister Pippa's weddings.

And the pair came armed with presents for their royal pals, with Mirka carrying what appeared to be two small wrapped gift boxes.

The couple, who wed in 2009, are parents to twin girls Myla Rose and Charlene Riva, eight, and Leo and Lennart, three.

After leaving the palace later on in the evening, Myla appeared to be carrying a drawing with her name scrawled on it.

Mother-of-four Mirka, 39, was wearing a cosy black jacket over a blue and white striped dress, with her hair coiffed to perfection.

The Federers were joined by Roger's mother Lynette, 65, on Wednesday and after returning to their hotel the adults were seen heading out again for dinner.

The youngest set of twins are bound to get along famously with Prince George, who turned four earlier this year and has recently started primary school at Thomas's Battersea.

Meanwhile Kate, 35, has only recently returned to royal duties after battling severe morning sickness during the first trimester her third pregnancy.

The youngest prince or princess will be fifth in line of succession to the British throne after Princess Charlotte, two.

The tennis-mad Duchess is a regular fixture in the Royal box at Wimbledon and is Patron of the Lawn Tennis Association.

Indeed, Kate and William watched as Federer thrashed Croatian Marin Čilić in the Wimbledon Men's Singles Final in July before presenting him with his 19th Grand Slam trophy.

The Cambridges have 22 rooms and two kitchens in their lavishly refurbished Kensington Palace apartment but Historic Royal Palaces recently submitted plans for an extensive 'iceberg basement' to added.

Federer and Čilić came face-to-face once again this week at the ATP Finals in London, with the Swiss champ securing a three-set win the day after his royal play date.

Prince Harry lives in nearby Nottingham Cottage where he is often visited by girlfriend Meghan Markle.

Earlier this year, devoted Roger praised his 'number one supporter' wife saying: 'She's been there when I had no titles and she's still here 89 titles later, so she had a big part to play in [his Australian Open win].'She knows it, I know it, everybody knows it. She's a mum number one and a wife, and only then later does she become the supporter.'

She stepped away from it a little bit after becoming super involved. I guess that was 2003, 2004 when she was right in the centre of the storm really.

'I didn't enjoy that role for her really because she had to say no too many times. She got a bad rap for it.'

She's the one who always tells me the truth and everything, so we go very well together.'