Meghan, 37, looked effortlessly chic in her striped blazer by L’Agence with a simple black T-shirt, blue jeans.

The new mum also donned a new necklace with an ‘A,’ appearing to pay tribute to her son Archie who was born in May.

She was joined by her Northwestern university friends Lyndsay Roth and Genevieve Hillis to watch the action from court one.

Serena, 37, and former actress Meghan, 37, are believed to have struck up a friendship at the Super Bowl in 2010.

The duchess has supported her friend at Wimbledon over the years, cheering her on at the Ladies’ Single Final with sister-in-law Kate last July.

Duchess of Sussex watches Serena Williams on court one. [Photo: PA]

Serena also attended Meghan and Harry’s wedding and organised her baby shower in New York earlier this year.

The tennis star was widely tipped to be Archie’s godmother, but Buckingham Palace said his godparents “in keeping with their wishes, will remain private.”

It’s believed that none of Harry and Meghan’s high profile friends have been chosen. The service will take place in a Private Chapel at Windsor Castle on Saturday 6 July.

ITV’s Royal Editor Chris Ship tweeted: “The godparents, I’m told are not public figures or celebrities, but private citizens. And therefore both they, and Harry and Meghan, don’t wish their names to be made public.”

Meghan is currently on maternity leave from official royal duties, but made her first public appearance after the birth for Trooping the Colour to mark the Queen’s official birthday in June.

She also joined her husband Harry at the New York Yankees versus Boston Red Sox baseball game last Saturday, where they received a personalised shirt for Archie.