Bound by eighteenth century law, the Queen signed an elaborate notice of approval, referred to as the “Instrument of Consent”, to officially recognise the marriage.
The Prince was required to ask his grandmother's permission under the Royal Marriages Act 1772, which rules that all descendants of George II must obtain the sovereign’s agreement before they marry.
Without the Queen’s consent, the marriage would be void.
The beautifully illuminated Instrument of Consent, which will be sent to the royal newlyweds to keep after next week’s wedding, is signed by the Queen in the top right corner.
It reads: "Now know ye that We have consented and do by these Presents signify Our Consent to the contracting of Matrimony between Our Most Dearly Beloved Grandson Prince William Arthur Philip Louis of Wales, K.G. and Our Trusty and Well-beloved Catherine Elizabeth Middleton.”
Tied to the bottom of the approval by gold braiding is the Great Seal of the Realm, the chief seal of the Crown, used to show the monarch's approval of important state documents.
The most official of all royal wedding memorabilia, the Instrument of Consent features decorative artwork chosen by the artist to represent the groom and bride-to-be.
A gold cipher of the couple's entwined initials beneath the prince's coronet represents the pair, but St James’s Palace has denied that this is the couple's official symbol.
A white lily embodies St Catherine of Siena, whose feast day falls on April 29th and with whom Miss Middleton shares her name.
Beneath it, a Welsh leek surrounded by William's white three-pronged second in line to the throne label, represents Prince William alongside a tiny red shell from the Spencer family Arms.
The heraldic symbol of a red dragon depicts Wales and the UK is present through the three floral emblems; the rose, thistle and shamrock.
The instrument also shows William’s blue and gold Order of the Garter belt, and a large gold E for Elizabeth.