King Charles III service: The green velvet robes, white ribbons and ostrich feathers of Scotland's highest chivalric order to be out in full force

Central to the Order’s ceremonial dress is the star insignia made up of a St Andrew’s cross with a green thistle on a field of gold surrounded by the Order’s motto, Nemo me impune lacessit.

A former motto of the Stuart dynasty, which translates as ‘no one provokes me with impunity’ – or ‘Wha daur meddle wi’ me? – it also serves as the motto for the Royal Regiment of Scotland.

A badge of St Andrew and his cross and a collar of thistles, which alternate with sprigs of rue, complete the vestments.

King Charles and Queen Camilla may choose to wear the robes of the Order of the Thistle to the St Giles’ service given the monarch last month made the Queen an “extra” of the order – an honour already held by The Duke of Rothesay, who will also attend the service, and Princess Anne.

At St Giles’ today, three Knights of the Order will take part in the uniformed, civic and chivalric procession into the cathedral. They are Lord Mackay of Clashfern (James Mackay, former Lord Advocate and Conservative peer), Lord Wilson of Tillyorn (David Wilson, former Governor of Hong Kong and Lord High Commissioner to the General Assembly of the Church of Scotland) and Lord Cullen of Whitekirk (William Cullen, former Lord Justice Clerk of Scotland).

Nine more knights and ladies will attend the service, including Sir Ian Wood, the oil industry leader and philanthropist, Lady Elish Angiolini, former Lord Advocate of Scotland, and Baron Narendra Patel, a retired obstetrician who built his career at Ninewells Hospital in Dundee and who played a key role in the coronation of King Charles III, will also attend.

The date of the foundation of the Order is not known, although legend says it was founded in 809 when King Achaius made an alliance with the Emperor Charlemagne, who reportedly used Scots bodyguards.

It is possible the Order may have been founded by James III (1488-1513), who was responsible for changes in Royal symbolism in Scotland, including the adoption of the thistle as the Royal plant badge.

James VII established the Order with a new statutory remit to reward Scottish peers who supported the king's political and Catholic aims. But after he was deposed in the so-called Glorious Revolution, no further appointments were made until the Order was revived by Queen Anne in 1704.

The motto of the Order, “Nemo me impune lacessit”, was the Latin motto of the Royal Stuart dynasty of Scotland from at least the reign of James VI when it appeared on merk coins.