In an intensely private ceremony, the Duke and Duchess of Cambridge's son Prince George will be christened today in front of close family and friends of his parents.
The Queen and Duke of Edinburgh are expected to be at the ceremony along with the Prince of Wales, who has become a grandfather for the first time, the Duchess of Cornwall and Prince Harry.
Kate's family - parents Carole and Michael Middleton and siblings Pippa and James - are thought to be invited, along with the godparents who, like the guests, have not been publicly named.
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The three-month-old infant, who will one day be king, will be baptised by the Archbishop of Canterbury, the Most Rev Justin Welby, in the little known Chapel Royal at St James's Palace this afternoon.
The Duke and Duchess of Cambridge are expected to break with tradition by picking close friends as Prince George's godparents.
William and Kate might pick Prince Harry, the Duchess's siblings James and Pippa Middleton or even the Duke's stepsister Laura Lopes - daughter of the Duchess of Cornwall - as the chosen ones, illustrating their close family ties.
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But they are rumoured to almost certainly selected either family or confidantes from their school and university days rather than opting for senior figures from within the royal court.
The Duke's best friend Thomas van Straubenzee, his old family friend William van Cutsem and William and Kate's former St Andrews housemate Fergus Boyd are all believed to be in the running.
Other contenders could include Kate's Marlborough College school friends, interior designer Emilia d'Erlanger, Catriona Foyle or Hannah Carter.
The royal couple have chosen celebrity portrait photographer Jason Bell to take the official pictures to mark the christening.
Bell is renowned for his images of Hollywood stars and rock and pop legends like Sir Paul McCartney, actress Scarlett Johansson and former England footballer David Beckham.
The photographs taken after the ceremony will be historic images that are expected to capture four generations of the royal family together.
The pictures will show the Queen with three future monarchs - Charles, William and George.
It will echo the picture taken in July 1894 during the christening of the future Edward VIII, showing the royal baby with his father, later George V, grandfather, the future Edward VII, and great grandmother, Queen Victoria.
Bell's images have been featured in the National Portrait Gallery and published in glossy magazines like Vogue and Vanity Fair.
In past decades, senior royal babies - the Queen, Charles and William - have been christened at Buckingham Palace.
But the Cambridges have chosen the Chapel Royal, where the coffin of the Duke's mother, Diana, Princess of Wales, lay before her funeral.
Princess Beatrice was the last well known royal baby to be christened at St James's Palace, in December 1988.
George will be christened in a replica of the intricate lace and satin christening gown made for Queen Victoria's eldest daughter, Victoria, the Princess Royal, in 1841.
The Earl and Countess of Wessex's son, Viscount Severn, became the first royal baby to wear the new robe at his christening in 2008.
In the past, godparents of royal babies high up the line of succession have mostly been selected from the older generations of royals, particularly grandparents and great-grandparents or from those with close connections to the royal establishment.
William's six godparents were: King Constantine II of the Hellenes; Lord Romsey; Sir Laurens van der Post; Princess Alexandra; the Duchess of Westminster; and Lady Susan Hussey, Lady in Waiting to The Queen.
The Prince of Wales's eight godparents were: his grandfather King George VI; his great-grandmother Queen Mary; his aunt Princess Margaret; his paternal great-grandmother Victoria, Dowager Marchioness of Milford Haven; his great-uncle the Hon David Bowes-Lyon; Lady Brabourne, daughter of Earl Mountbatten of Burma; and his great-uncles King Haakon of Norway and Prince George of Greece.
The Queen's six godparents were: her paternal grandparents King George V and Queen Mary; her maternal grandfather the Earl of Strathmore and Kinghorne; her aunts Mary, Princess Royal, and Lady Elphinstone; and her great-great-uncle Prince Arthur, Duke of Connaught.