Father-to-be the Duke of Sussex smiled broadly and appeared relaxed at an Anzac Day service as he awaits the birth of his first child.

With Harry leaving heavily pregnant wife the Duchess of Sussex behind at their new Windsor home, Frogmore Cottage, to carry out the official royal engagement, bookmakers are now predicting May, rather than April, will be the royal baby's birth month.

William Hill spokesman Rupert Adams said: "We were as surprised as everyone else that Harry decided to attend a public event as we assumed the baby was imminent.

"We are now odds on that baby will not arrive until May."

William Hill has it at 4/5 that the baby will be born in May, while Coral now has May at 1-3, followed by April at 2-1 and June as the outsider at 11-4.

The duke was a last-minute addition to the royal line-up in Westminster Abbey, where he joined his sister-in-law, the Duchess of Cambridge, on Thursday afternoon.

Catherine, who looked chic in a teal Catherine Walker coat and Rosie Olivia hat, was pictured laughing as she chatted to Harry, dressed in a suit adorned with medals, as they made their way into the Abbey.

Harry had always planned to attend the service and was said to be pleased to be able to join the congregation, but Buckingham Palace only confirmed a few hours before that he would be going.

The duke's name was not printed in the order of service in case Meghan went into labour with baby Sussex and he was unable to be there.

His presence suggests Meghan is showing no signs so far of giving birth soon, with the duke able to be parted from her to attend the hour-long memorial in central London.

American former actress Meghan is likely to be at home in the couple's newly refurbished Frogmore Cottage in the sanctuary of the Windsor Estate.

The duchess's mother, Doria Ragland, is said to have flown from Los Angeles to stay the couple as they await the imminent birth of the baby, which will be Doria's first grandchild and an eighth great-grandchild for the Queen.

The name Grace is one of the new favourite names at the bookmakers for a girl, in joint first place with Diana at 6-1 at Coral, with Arthur 8-1 favourite for a boy.

Punters are still predicting a girl, while Coral has also seen a flurry of bets on Meghan giving birth to twins, with odds of 4-1.

Coral's John Hill said: "The royal baby now looks more likely to arrive in May according to the betting and that is what punters have been rushing in to back over the last 24 hours.

"Grace continues to be the most popular selection in our name betting and it is the girls' names which are seeing the most money."

The arrival of Baby Sussex will mean Meghan will still be tending to her newborn when US president Donald Trump makes his state visit to the UK on June 3.

Harry could, however, be called upon to meet Mr Trump when the controversial American businessman is entertained by the Queen at Buckingham Palace.

William Hill has odds of 3-1 that seventh in line to the throne Baby Sussex will be introduced to Mr Trump during his stay.