Knight of the Thistle: How the Royals and others have grasped the nettle By BRIAN FERGUSON Published on Wednesday 4 July 2012 00:00 PRINCE William will be installed as a Knight of the Thistle in Edinburgh tomorrow, but what are the origins of Scotland's highest award? TUCKED away in a corner of one of Edinburgh's best-known landmarks, there is little to alert the thousands of Royal Mile visitors to its presence - or historical significance. The chapel added to St Giles" Cathedral just over a century ago is not only one of Scotland's most breathtaking architectural treasures, it is also the spiritual home of Scotland's "ancient order of chivalry" - said to date back to the ninth century - which is still the highest honour this country can bestow. It is here tomorrow that Prince William will be installed into the Order of the Thistle after the Queen appointed him a new royal knight of the order last month to mark his 30th birthday. The Earl of Strathearn - as the prince is known in Scotland - will join the 16 other existing knights, as well the Queen, the Duke of Edinburgh, his father and the Princess Royal in the order which has been running in continuous form since 1687. He will join other Knights of the Thistle, including Lord Steel, former presiding officer of the Scottish Parliament; Lord Robertson, the former Scottish Secretary; Lord Mackay of Clashfern, the former Lord Chancellor, and Lady Marion Fraser, the former Scottish Opera director, who is officially known as a "Lady of the Thistle." But how many of the hundreds of admirers expected to flock to the Royal Mile for a glimpse of the prince on his big day will realise the mysterious origins of the honour that is being conferred on the prince, its revival by a succession of monarchs and its strange traditions? Historians are divided on the origins of the order, although the tradition is thought to date back to 809, when Achaius, the Pictish King of Scots, formed an alliance with Emperor Charlemagne of France. Some accounts believe Achaius established the order in 786 after winning the Battle of Athelstaneford in East Lothian when he reputedly saw the cross of St Andrew in the sky. According to St Giles" Cathedral's official account, the order is most likely to date back to the 15th century, when James III adopted the thistle as the royal plant badge. Its guide to the chapel states: "There are various pictures of the king or of the royal coat of arms from this era showing a ceremonial collar of thistles, suggesting the existence of a kind of royal order." Richard Welander, head of collections at Historic Scotland, said: "It is known that James VII of Scotland issued a statute which revived the Order of the Thistle in 1687. In Edinburgh Castle, if you go into the Crown Room, you can actually see very early evidence in the bejewelled St Andrew Jewel, which is believed to date from the following year. It is an oval-shaped disc studded with diamonds with a thistle in the middle. However there is evidence that the Order of the Thistle may have begun much earlier. For example, it is known that James V bestowed the "Order of the Burr" or "Order of the Thissil" on Francis I of France back in 1535 and there does appear to be evidence that it existed in some form in the 1400s. However, the very origins of the order appear lost in the mists of time. The fact it is such an ancient and noble order certainly adds to the whole gravitas of it. When James VII decreed that the Order of the Thistle should be revived as a symbol to reward Scottish peers who supported the king's political and religious aims, he chose to appoint 12 knights. Mr Welander added: "The original number chosen by James VII when he revived the order was meant to symbolise the 12 apostles of Christ and there has always been a strong religious element to the order." New members are sworn in by taking the following oath: "I shall fortify and defend the Christian religion, and Christ's most holy evangel, to the utmost of my power. I shall be loyal and true to my Sovereign Lady, the Queen, and the members of this order. I shall maintain the honour and dignity of the most ancient and most noble order of the thistle to my best power if God let. I shall never bear treason about in my heart against our Sovereign Lady, the Queen, but shall discover the same to her. Although the order stretches back at least several centuries, the chapel itself was built in 1910, although in the style of the high gothic architecture of the 15th century. Its highlights include 100 "bosses" carved into its ceiling, each of the knights" seats with their own unique carvings, the chapel's angels playing traditional Scottish instruments like the bagpipes and the fiddle, and the stained glass window bearing the ancient motto of Scotland, "nemo me impune lacessit" - "no-one provokes me with impunity." Bruce Gorie, secretary to the Office of the Lord Lyon, which is responsible for state ceremonies in Scotland, said: "It's a very unusual honour because the appointments to the Order of the Thistle are made directly by the Queen. It is the Scottish equivalent of the Order of the Garter, but fewer people are installed into the Order of the Thistle. The number of knights is always limited to 16 these days, as well as the Royal Knights, and a new one is appointed whenever a knight passes away. It's the same ceremony tomorrow that is held each time there is a new knight of the order, with a procession from the Signet Library led by Her Majesty's Officers of Arms. The style of the event won't really have changed much at all over the last 100 years when it has been held at the Thistle Chapel. Tomorrow's ceremony will get underway at 11am after the procession from the Signet Library. Each knight will be wearing identical outfits - a dark green velvet mantle and a black velvet hat adorned with white ostrich feathers. Although there will be relatively little for the crowds to see compared to most state occasions, at 12.30pm a parade of pipers will set off from the City Chambers to the Scottish Parliament, where entertainment is being laid on as part of a celebration of the Queen's Diamond Jubilee organised by the Scottish Government. Edinburgh's Lord Provost Donald Wilson, also a Lord Lieutenant, said: "Honouring traditions and safeguarding our heritage are key to the values of Scotland's capital city and I am sure there will be large crowds of wellwishers outside St Giles" Cathedral. As the Queen's representative in Edinburgh, I would like to offer the city's warmest congratulations to Prince William on his installation as a Knight of the Thistle.