Can someone be knighted twice? Sir David Attenborough receives rare honour

Sir David Attenborough has been given a rare honour for his services to broadcasting and conservation.

The environmentalist, 96, was appointed Knight Grand Cross of the Order of St Michael and St George at a ceremony on Wednesday.

The honour has been described by some as a 'second knighthood', although that isn't strictly accurate.

Sir David's new title is distinct from – and more prestigious than – the knighthood he received from the Queen in 1985.

Here is everything you need to know about what it means.

What does David Attenborough's new title mean?

The Order of St Michael and St George recognises service in a foreign country, or in relation to foreign and Commonwealth affairs.

Sir David is one of 120 people with the title Knight/Dame Grand Cross (GCMG), and one of the few not to be a diplomat.

The Planet Earth broadcaster, whose career spans seven decades, was appointed to the rank in the Queen's Birthday Honours ahead of the Platinum Jubilee.

He officially joined the order at an investiture ceremony at Windsor Castle attended by the Prince of Wales.

The order also consists of the Queen, the Duke of Kent and two other ranks: Knight/Dame Commander (KCMG/DCMG) and Companion (CMG).

Earlier this year, James Bond star Daniel Craig was made a Companion – the same rank as the fictional spy.

How does the honours system work?

Honours as part of orders of chivalry have been given by monarchs since the Middle Ages.

Nowadays, the UK's honours system recognises people who have "made achievements in public life" and "committed themselves to serving and helping Britain".

Honours are announced twice a year – at new year and in June on the Queen's official birthday.

Any member of the public or an official body can nominate someone for an honour.

UK nationals and citizens of 15 Commonwealth "realms" of which the Queen is head of state are eligible for nomination.

People living or working overseas, whose achievements were made in another country or in the UK and have a significant international element, can be nominated too.

Non-British or Commonwealth country citizens can be considered for honorary awards.