The Duke and Duchess of Cambridge have been given a joint "conjugal" coat of arms by the Queen to represent them as a married couple, as they announce the date of Prince George's christening.
The royal baby will be christened by the Archbishop of Canterbury, the Most Rev Justin Welby, on Wednesday October 23 at the Chapel Royal, St James's Palace, Kensington Palace announced today.
Meanwhile, the couple's marriage was acknowledged formally by the Queen as she presented them with a coat of arms.
Designed by The College of Arms in London, Conjugal Arms traditionally show the separate shields of a Royal husband and wife, side by side.
On the left of the design is the Duke's version of the Royal Coat of Arms granted to him by The Queen on his 18th birthday. On the right is the Duchess’s shield from the Middleton family Coat of Arms, granted to the family in 2011 ahead of her marriage.
A spokesman for Kensington Palace said: "The Conjugal Arms will be theirs forever, but as their circumstances and roles alter, elements of the accoutrements around the shields may change. In addition to their Conjugal Arms, Their Royal Highnesses also retain their own Coats of Arms to represent themselves as individuals."
It is the third new coat of arms for the Duchess in the space of two years.
Just days before the Royal wedding in 2011, the Middleton family were awarded their own coat of arms featuring acorns and a gold chevron. The Duchess herself helped design that emblem, suggesting three acorns for the three Middleton children.
The Middleton family crest was commissioned by Michael Middleton from the College of Arms, a branch of the royal household, and cost £4,400.
After the royal wedding the Duchess was granted her own Coat of Arms by the Queen, made by placing her father’s Arms beside those of her husband in what is known as an impaled Coat of Arms.
The shield on the left of the new Conjugal Coat of Arms, representing the Duke of Cambridge, shows the various Royal emblems of different parts of the United Kingdom: the three lions of England in the first and fourth quarters, the lion of Scotland in the second and the harp of Ireland in the third.
It is surrounded by a blue garter bearing the motto Honi soit qui mal y pense (‘Shame to those who think evil of it'), which symbolises the Order of the Garter, of which the Duke is a Knight Companion.
The Duchess of Cambridge’s shield on the right shows the Middleton family Arms, technically known as "Per pale Azure and Gules a Chevron Or cotised Argent between three Acorns slipped and leaved Or".
Per Pale means that the Shield is divided vertically with one half blue (azure) and the other half red (gules). A Chevron Or means the gold chevron across the centre of the shield. There are smaller white chevrons, or cotises, above and below the gold chevron, symbolising snow-capped mountains from the Middletons' skiiing holidays. Slipped means ‘with a stalk,’ so the final part of the blazon – and distinguishing feature of the Shield – means three acorns with gold stalks and leaves.
Acorns were chosen because the Middleton family home at the time of the royal wedding was surrounded by oak trees.
For its placement in the conjugal Arms, the Duchess of Cambridge’s shield is surrounded by a Wreath of Oak, to balance out the Duke’s garter. This is traditional for Royal Spouses who are not themselves entitled to surround their Arms with an order of chivalry.
Both shields are supported by the Duke of Cambridge’s supporters of the Royal Lion and Unicorn wearing a three pointed collar, known as a label. The label has a red escallop shell derived from the Spencer Coat of Arms which has been used by the Duke's ancestors on his mother's side for centuries.
Conjugal Coats of Arms are a royal tradition, and have been granted in the past to the Queen and the Duke of Edinburgh, and the Prince of Wales and Duchess of Cornwall, though they are rarely used.
Thomas Woodcock, Garter King of Arms, said the new design is most likely to be used on plaques when the Duke and Duchess jointly perform official openings.
He said: "The Duchess did come in when we were designing it and she said that on the compartment, which is the thing they stand on, she liked the grass darker at the back and paler at the front. It's a small point, but something she picked up on."