KING Charles has appointed the Duke of Edinburgh to the Order of the Thistle to mark his 60th birthday. 

Appointments to the order are entirely in the personal gift of the King and do not require any prime ministerial advice.

The new appointments are effective from Sunday and an installation process will take place over the Summer. 

Charles previously made Edward the Duke of Edinburgh to mark his 59th birthday.

What is the 'Order of the Thistle'?

The Order of the Thistle is the "highest honour in Scotland", and across the UK its "prestige" is second only to the English Order of the Garter, according to the royal family's website.

The order comprises 16 knights or ladies and the monarch is the Sovereign of the Order, so any appointments are his "personal gift".

The royal family website further states that The Order of the Thistle recognises "Scottish men and women who have held public office or who have contributed in a particular way to national life".

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Republicans criticised “cronyism with a crown on top” when Charles bestowed the honour on his wife Camilla – who was born in London – last year.

William, the “Prince of Wales” and “Duke of Rothesay”, is also in the order, as is Princess Anne.

There are various peers and members of the aristocracy in the order, such as Richard Scott, the “Duke of Buccleuch”, and David Ogilvy, the “Earl of Airlie”.

Other names in the order include SNP politician and former Holyrood presiding officer George Reid and Elish Angiolini, the former lord advocate of Scotland.

The Order of the Thistle was formally established with a statutory foundation under the rule of Scotland's James VII in 1687. He claimed he was "reviving and restoring" an older order.

According to legend, the order dates back to the year 809AD, but it is possible that it was actually founded by Scots King James III, who was "responsible for changes in royal symbolism in Scotland, including the adoption of the thistle as the royal plant badge", according to the royal family website.