The menfolk were equally smartly dressed, though barely a kilt was to be seen. For them, sharp suits and morning coats were the order of the day.
Around 1000 people, all clutching their invitations and photo ID, crammed into the cathedral to witness Prince William – known as the Earl of Strathearn while in Scotland – being installed by the Queen as a Knight of the Most Ancient and Noble Order of the Thistle.
Inside the 12th century cathedral, there was a hushed silence before the service began with a fanfare of trumpeters of the Band of Her Majesty's Royal Marines Scotland. People craned their necks to watch the procession as velvet-cloaked Royal Poursuivants, Heralds, the Green Rod, Lord Lyon and 15 existing Knights of the Thistle – including Lord Robertson of Port Ellen, Lord Steel of Aikwood, Lord Mackay of Clashfern and Lord Macfarlane of Bearsden – made their way to the Thistle Chapel.
Lady Marion Fraser and the Princess Royal were also present, having become Ladies of the Thistle since the Queen decreed in 1987 women could also join the Order.
Then came Prince William, the tallest and youngest of them all, wearing his own dark green velvet cloak and clutching his feathered hat in his hand. Behind him walked Prince Philip and the Queen, accompanied by her page of honour, their great-grandson Arthur Chatto.
Their expressions were as solemn as the event. Then, as two elderly Archers guarded the archway at the entrance to the chapel, we heard the disembodied voice of William over the public address system as, out of sight of the congregation, he repeated the words spoken to him by the Dean of the Thistle, the Very Rev Gilleasbuig Macmillan.
As the procession made its way back inside the Cathedral, Prince William sat down beside his wife the Countess of Strathearn.
The service at St Giles was followed by a spectacular celebration of pipe music, drumming and dancing on the Royal Mile as bands, dancers and drummers from across Scotland were led down to the Scottish Parliament for a grand finale.
The royal party left the Signet Library after lunch and also headed down the Royal Mile towards the Palace of Holyroodhouse, with the Duchess of Cambridge, as she is better known, wearing a pale yellow coat dress designed by Emilia Wickstead, with a Whiteley hat and carrying a Strathearn tartan wrap.
Numerous onlookers waved Saltires and Lion Rampants as the royal family passed.
First Minister Alex Salmond said: "Scotland has always had a special relationship with Prince William and therefore it is fitting he should receive the Most Ancient and Most Noble Order of the Thistle, which represents the nation's highest honour. This magnificent ceremony is one of the many highlights of a particularly busy royal week this year when we can pay tribute to our Queen of Scots and the Royal Family."
The Queen's week in Scotland concludes today with engagements in Perth.