Queen's joy at Royal baby news

Her Majesty and the rest of the Royal family are said to be delighted that William and Kate are expecting their first baby.

The Duchess spent the night in a London hospital with severe morning sickness as messages of support and congratulations flooded in from all over the world.

William was expected to spend the day at his 30-year-old wife's bedside at the King Edward VII hospital.

The Prince, also 30, drove his wife to the hospital from Bucklebury in Berkshire, where her parents Michael and Carole Middleton live.

Kate, who is suffering from the condition known as hyperemesis gravidarum, is expected to remain there for a few days.

The Duchess had a number of engagements this week but they have all been cancelled, said St James's Palace.

It is understood that the pregnancy has not passed the 12-week point and the announcement was prompted by the Duchess's medical condition.

Doctors will replace lost fluids to keep dehydration at bay, boost her nutrition and monitor her progress.

Speculation about a Royal pregnancy has been rife over the past few months and babies were the topic of conversation when William and Kate visited Cambridge last week for the first time as a married couple.

The Duke, an RAF search and rescue pilot, was given a tiny baby romper suit made by well-wisher Samantha Hill which was decorated with a picture of a helicopter and the words 'Daddy's little co-pilot'.

The baby theme continued when Kate met Tessa Davies, aged 35, from Cambridge, who had given her son five-month-old James the middle name William in honour of the Duke and had brought him to meet the Royal couple. The Duke and Duchess have made no secret of their desire to start a family and in September during a Diamond Jubilee visit to Singapore the Duke revealed he would like to have two children.

Their first-born will be third in line to the throne, regardless of whether it is a boy or a girl. Messages of congratulations have poured in from across the globe as well as from across the West Midlands and Staffordshire.

A statement released by a St James Palace spokesman read: "The Queen, the Duke of Edinburgh, the Prince of Wales, the Duchess of Cornwall and Prince Harry and members of both families are delighted with the news."

The palace would not say when the Royal couple became aware of the pregnancy, only saying "recently". Even the Queen and other senior Royals were taken by surprise because Kate and William had not yet broken the news although it is understood that they told Kate's parents over the weekend.

There is speculation that they had intended to tell the rest of the Royal Family on Christmas Day at Sandringham.

Prime Minister David Cameron led the congratulations from the nation when he said: "It's absolutely wonderful news and I'm delighted for them. I'm sure they will make absolutely brilliant parents, and I'm sure everyone around the country will be celebrating with them."

Councillor Christine Mills, mayor of Wolverhampton, said: "It is wonderful news that they are expecting a baby and rounds off a perfect year for the Royal family."

Mayor of Stafford Councillor Bryan Cross said today: "We are absolutely delighted for them and the borough will be sending greetings. It's a perfect end to the year, and what a year we have had with the Jubilee, Olympics and Paralympics and now a Royal announcement."

Kate's visit to her old prep school on Friday afternoon was her last public engagement. She appeared well and had lunch at St Andrew's school in Pangbourne, Berkshire, with pupils and staff.

A spokeswoman for St Andrew's – where Kate showed off her hockey skills in an Alexander McQueen frockcoat and three-inch-high calf-length boots – said they had "no inkling at all" that she was expecting.

Tony Little, headmaster at Eton College, where the Duke went to school, added his congratulations, saying: "We are delighted with the news and wish the Duke and Duchess of Cambridge every happiness."

Although the sex of the baby is not yet known, whatever name the Royal couple choose is likely to set a trend. Bookmaker William Hill said favourite names are Frances and John, both at 9/1, while Charles, Victoria and George are 10/1.