They look just like any other young couple taking the train back home after a break in the country.

But look closely and you'll see that the couple dressed casually in jeans , making their way across the concourse at Kings Cross are in fact the future King and Queen.

Prince William and Kate Middleton had commuters doing a double take as they passed through the rush hour crowds on Friday with their cocker spaniel, Lupo in tow.

13-month-old Prince George was noticeably absent and is thought to have remained at Kensington Palace with his nanny, Maria Borrallo, during his parents' break in the country.

The couple and Lupo were accompanied by an entourage of protection officers and were collected by a waiting people carrier after leaving the train.

The duke and duchess, both 32, had travelled on the scheduled train from King's Lynn where they had been staying at Anmer Hall, their home on the Queen's Sandringham estate.

They have been in Norfolk for the past fortnight, overseeing the final stages of a £1.5million refurbishment of the hall, where they will be spending more time when Prince William starts his new job as a pilot for the East Anglian Air Ambulance.

The royal couple had recently taken an undercover train ride.