Prince William, Kate Middleton spend anniversary at Buckingham Palace

Prince William and Kate Middleton celebrated their fourth wedding anniversary at a very familiar royal residence — Buckingham Palace. In 2011, the couple greeted the nation from the palace balcony and shared their first public as newlyweds in front of cheering crowds. On Wednesday, William and Kate were spotted driving into Queen Elizabeth’s residence.

Photo: Getty Images

It is not yet known what the purpose of their visit was, but if they took Prince George with them, the royal tot may well have been enjoying a swimming lesson in the palace pool. He’s known to swim regularly at his grandmother’s London palace.

Kate, 33, is thought to be a few days overdue with her and William's second baby, and her second trip to Buckingham Palace in as many days has led royal watchers to believe that she won't go into labor just yet. The pregnant Duchess was said to be driving herself into the palace, with William also in the car.

On Tuesday, Kate was spotted at the wheel bringing George, along with his Spanish nanny Maria Teresa Turrion Borrallo , for a dip in the pool. The trio was joined by their security detail.

Last summer Kate revealed that her 21-month-old toddler is a big fan of swimming and that she regularly takes George to the pool at Buckingham Palace. On this occasion, however, it was Maria who looked after the future king in the water.

Photo: Getty Images

Speaking to former world champion swimmer James Hickman, Kate was overheard telling the athlete that George "loves the water and he grabs things to splash with."

The royal darling is set to become a big brother any day now to a little prince or princess. William, 32, and his wife Kate have chosen to leave the gender of their second child a surprise, just as they did before George was born.

Fans of the couple have been waiting patiently outside St. Mary's Hospital where Kate is set to give birth. Ready for a boy or girl, they have come prepared with signs reading, "It's a Prince" and "It's a Princess."

While Kate has previously said that her due date was "mid-to-late April", it looks increasingly likely that the baby will arrive at the beginning of May. Parking restrictions outside the hospital have been extended an additional five days until May 5, from April 30 that was on the original signs.

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