Photographers and television crews mark out positions in front of the door to the Lindo Wing of St Mary's Hospital, where Britain's Catherine, Duchess of Cambridge is due to give birth in central London July 2, 2013.[Photo/Agencies]

Photographers are camped outside the hospital, social media are buzzing, and stores are touting baby goods ahead of the expected arrival this week of the future heir to the British throne.

Britain is officially on baby watch with Prince William and his wife Kate Middleton awaiting the imminent arrival of their first child who will be third in line to the throne.

The couple, known as the Duke and Duchess of Cambridge since their sumptuous royal wedding in April 2011, announced last December that a baby was on its way after Kate was admitted to hospital for four days suffering from severe morning sickness.

With the due date looming, the duchess stopped official duties last month while Prince William, a helicopter search-and-rescue pilot and grandson of Queen Elizabeth, is on standby at an air force base in north Wales to rush back to London.

The couple have remained vague about the exact date the baby is due other than to say mid-July and the arrival will be announced in a combination of the traditional and modern - via Twitter, websites and with a notice outside Buckingham Palace.

However in a sign the baby's arrival was getting closer, royal officials announced that the baby would be known by its given name and would have the title His or Her Royal Highness Prince/Princess of Cambridge.

The Palace also revealed on Monday that the Queen's granddaughter Zara Phillips and her husband, rugby player Mike Tindall, were expecting their first baby in the new year.

Joe Little, managing editor of Majesty Magazine, said the duke and duchess were a private couple and, while aware of the massive global interest, were trying to limit public exposure.

"Privacy is key for Prince William as he saw the way his mother, Princess Diana, suffered at the hands of the paparazzi, and he wants to make sure this does not happen to his wife or his own children," Little told Reuters.

The baby is to be born in the private Lindo wing of St. Mary's Hospital in London where Prince William was born 31 years ago. Princess Diana, who died in a car crash in 1997 after splitting up with Prince Charles, also had Prince Harry there.

Prince Charles, the heir apparent, was present for the births of his sons and Prince William, second in the line to the throne, plans to be there for his first child.