No due date has been announced for the royal birth, which is expected during the second half of this month.

With Prince George and Princess Charlotte, Kate gave birth just over five weeks after going on maternity leave.

She went on maternity leave for her third child on March 22, so this suggests the baby might put in an appearance around April 27 or 28.

The birth might even end up being a double celebration if it falls on William and Kate's seventh wedding anniversary, which falls on April 29.

Kate is thought to have gone overdue with both George and Charlotte, so a lot will depend on whether the same happens this time.

She may have scheduled her final engagements closer to her due date this time, suspecting the baby is unlikely to arrive early.

With Charlotte, parking restrictions outside the Lindo Wing of St mary's Hospital in London went up on April 15 and she arrived 17 days later.

For George, the traffic notices were posted on July 1 and the prince arrived 21 days later.

Looking at these timelines, with parking restrictions starting on April 9, the new baby could arrive as late as April 30.

The Duke of Cambridge, however, told Ringo Starr during an investiture on March 21 that the baby is due 'any minute now'.

Other suggestions have cited St George's Day - April 23 - as Kate's possible due date.

The baby might even end up sharing a birthday with their great-grandmother the Queen, who turns 92 on April 21.

Princess Charlotte might prefer to keep her birthday to herself on May 2 - or alternatively see it as the best birthday present ever if the baby arrives on the day she turns three.

Kate welcomed her first born, George, 38 days after her last public appearance in 2013.

She attended the Trooping the Colour parade in London on June 15 2013 and George was born at the Lindo Wing on July 22.

Princess Charlotte - who was meant to be born in April - finally arrived on May 2 2015 - 37 days after Kate's final engagement.

In 2015, the Duchess carried out her last public engagement on March 27 when she met Baroness Lawrence at the Stephen Lawrence Centre and saw projects run by the charity eXceL Project in London.