The funeral of Queen Elizabeth II will take place on Monday 19 September.
Before then a series of protocols will be followed as part of the mourning period for the late monarch.
These protocols are a part of a series of events known as Operation Unicorn which come into effect alongside Operation London Bridge.
One of these events is known as the Vigil of the Princes but what is a Vigil and what is the meaning behind the tradition?
What is a Vigil?
A vigil is a period of devotional watching or observance which takes place the night before a key landmark or event.
The term is derived from the Latin word ‘vigilia’ which means wakefulness and is associated with a public occasion of mourning for a key figure.
Such gatherings are seen as a powerful way of bringing people together to honour someone’s life. They are often held in the evening after sunset.
What is the Vigil of the Princes?
The Vigil of the Princes is a tradition within the royal family which has been honoured since the death of King George V in 1936.
The Vigil of Princes is normally held by the senior male figures in the royal family.
The tradition has been held on two occasions: the first was for King George V in 1936 and the second was held for Queen Elizabeth, the Queen Mother in 2002.
The Vigil of the Princes was not held following the death of King George VI in 1952 as he didn’t have any sons and his grandchildren were too young at the time.
What happens during the Vigil of the Princes?
The Vigil of Princes is held to commemorate the monarch and show respect.
During the vigil the senior members of the royal family stand around the coffin facing outwards. The tradition usually lasts around 10 minutes.
During Queen Elizabeth’s mourning period a vigil was held at St Giles Cathedral in Edinburgh. King Charles, The Duke of York Prince Andrew, The Earl of Wessex Prince Edward and The Princess Royal stood facing outwards around their mother’s coffin.
Members of the public filed past to pay their respects as the four siblings stood in silence with their heads bowed.
Princess Anne, the Princess Royal, became the first female member of the royal family in history to take part in the vigil. All of the siblings except Andrew wore a military uniform.