Royal Marine commandos are the sea soldiers of the Royal Navy and their motto 'Per Mare, Per Terram' means 'By Sea, By Land'.
The Latin phrase symbolises the Royal Marines' dual role as an 'elite amphibious fighting force', operating both on board ships and ashore.
It is believed to have been used for the first time in 1775 during the American Revolutionary War.
The term was used by the Duke of Sussex when he signed off a tribute to his grandfather, the Duke of Edinburgh, following his death aged 99, who he described as "a man of service, honour and great humour".
Both Prince Harry and Prince Philip have held the ceremonial title of Captain General Royal Marines.
Watch: Royal Marines put Future Commando Force concepts to the test, during Littoral Response Group (Experimentation) (LRG(X)) in Cyprus.
Royal Marines wear the highly coveted green beret, which takes much work to earn.
The rigorous training that recruits undergo at the Commando Training Centre Royal Marines (CTCRM) in Lympstone is widely recognised as some of the toughest and longest of its kind in the world.
The Royal Marines are currently undergoing a dramatic modernisation programme to become the Future Commando Force (FCF).
It has been described by the Royal Navy as the most significant transformation and rebranding programme since the Second World War.
Cover image: Royal Marines test their skills in the Corsham Tunnels (Picture: Royal Navy).