Babies on the brain, Will and Kate?

On Thursday, Prince William and Kate Middleton made their second public appearance in London following a long hiatus.

Inside a reception to celebrate the Scott-Amundsen Centenary Race to the South Pole, in support of The Royal British Legion, the Duke and Duchess of Cambridge made a beeline for one very special attendee: a three-week old baby boy named Hugo.

According to one onlooker, the royals, who celebrate their one-year wedding anniversary this weekend, made a fuss over Hugo.

"Kate and William cooed over Hugo," the observer tells Us Weekly. "Both of them were commenting how cute the baby was and they were both googly-eyed."

William, 29, "even cuddled him!" the onlooker marvels. "So cute!"

For now, however, the Duchess, 30, is not with child. She looked stunning and thin as ever in a blue tweed suit by designer Rebecca Taylor, accessorized with a blue clutch and heels, plus a $40 enameled poppy brooch. The future Queen sipped a glass of water at the event, where she and her husband celebrated a group of soldiers who recently recreated the famous Scott-Amundsen race to the South Pole during a visit to London.

The arduous challenge has helped raise millions of dollars for the Royal British Legion and the Battle Back Centre, Lilleshall, which helps wounded, injured and sick service people recover.

That wasn't the couple's only errand on Thursday.

That morning, William and Kate made a private visit to London's MI6 headquarters, where they met with spies at the Secret Intelligence Services in Vauxhall, a palace source confirms to Us.

"Their visit was top secret," the source says.