Prince Harry, Meghan, Prince William and Kate attend secret dinner

Prince Harry and Meghan Markle have joined Prince William and Kate Middleton at a “secret” dinner event.

The royal quartet chatted to presenter Anita Rani and singer Tom Walker the Royal Foundation’s autumn dinner, at Victoria House in London.

But the glamorous bash had been “kept under wraps” by Kensington Palace.

Pictures from dinner aren’t usually released to the public but performer Tom shared pictures from inside the party on his Twitter and Instagram accounts.

The Scottish musician wrote: “I had the absolute honour of performing for and meeting the Duke and Duchess of Cambridge & the Duke and Duchess of Sussex for the annual @KensingtonRoyal Royal Foundation dinner.

“Thanks to the talented @Thatsingingbird from @wearefulleffect for joining me for my last song.”

Tom is seen chatting to the Royal couples at the party and posing with the Duke of Cambridge.

Kate was wearing an elegant red Preen dress she had previously worn on her tour of Canada, continuing her new custom of recycling old outfits.

Meghan — who is expecting a baby in spring — wore a strapless navy Roland Mouret dress, which retails at £2195 ($A3844) and carried a navy UFO clutch.

The foundation was set up by the two Princes in 2009 as a channel for their charitable work in many areas, including mental health, wildlife and conservation, young people and the armed forces.

Since their respective weddings, Meghan and Kate have also become patrons.

The photos emerged after reports that Prince Harry and his wife, Meghan may leave Kensington Palace altogether amid rumours a senior royal is refusing to give up their home.

The Duke and Duchess of Sussex officially set up home in the modest two-bedroom cottage, Nottingham House, after tying the knot in May.

Prince Harry lived there while single and it was here he proposed over a roast chicken.

But with baby number one on the way, the royal couple are said to be eyeing up a larger property to raise their family in.

Earlier this week, the royal family gathered to celebrate Prince Charles’ 70th birthday with a tea party and a banquet in Buckingham Palace.

In two official photographs released to mark the Prince of Wales’s milestone, Charles is shown surrounded by his wife Camilla, two sons William and Harry and three grandchildren.

A fourth grandchild is on the way after Prince Harry’s wife Meghan, an American former TV actress, announced her pregnancy following the couple’s Windsor Castle wedding this year.