Dame Sandra Mason, who will become Barbados's first president in a ceremony later, is pictured in 2018
Barbados is preparing to lower the Royal Standard for the final time this morning as the Caribbean island becomes a republic.
The Queen sent a message of congratulations to Dame Sandra Mason, the woman who will replace her as Head of State.
Dame Sandra will be sworn in as the island nation's first president at 400 years of loyalty to the British Crown in a ceremony in the capital Bridgetown attended by Prince Charles.
In her message, the Queen wrote: 'On this significant occasion and your assumption of office as the first President of Barbados, I extend my congratulations to you and all Barbadians.
'I first visited your beautiful country on the eve of independence in early 1966, and I am very pleased that my son is with you today.
'Since then, the people of Barbados have held a special place in my heart; it is a country rightfully proud of its vibrant culture, its sporting prowess, and its natural beauty, that attracts visitors from all over the world, including many people from the United Kingdom.'
The Prince of Wales will highlight the shared goals and enduring bonds between Barbados and the UK during this morning's ceremony.
Charles will also tell the nation it is 'important' for him to attend the event to 'reaffirm those things which do not change' as the major constitutional shift takes place.
The heir to the throne will deliver his address just after midnight, local time, as Barbados begins a new chapter in its history on November 30 - the 55th anniversary of independence from Britain.
The Prince of Wales is greeted by Dame Sandra Mason, who will become President later, as he arrived in Barbados on Sunday
Barbados's decision to remove the Queen as head of state will be watched closely by other members of the Commonwealth especially in the Caribbean region.
Prime Minister Boris Johnson said the UK and Barbados will remain 'steadfast friends and allies' with 'a partnership built to last'.
'As Barbados turns a new page in its history and becomes a republic, I am proud to celebrate the enduring relationship between our two countries,' he said in a statement.
'We will remain steadfast friends and allies, building on the longstanding kinship and connections between our people and the unique bond of the Commonwealth.
'Ours is a partnership built to last, as we tackle shared global challenges like the climate crisis and global recovery from the pandemic together.'
During the ceremony in National Heroes Square, Charles is expected to say: 'As your constitutional status changes, it was important to me that I should join you to reaffirm those things which do not change.'
Locals joined in a 'Pride of Nationhood' celebration on Monday evening, the country's last day with the Queen as head of state
Bridgetown was in party spirit late on Monday ahead of the swearing in of Dame Sandra Mason as the nation's first president
He will go on to give examples of the ties that will remain - 'the close and trusted partnership between Barbados and the United Kingdom as vital members of the Commonwealth' and 'our common determination to defend the values we both cherish and to pursue the goals we share'.
Charles is also expected to celebrate the cultural, social and economic bonds between the UK and Barbados, 'the myriad connections between the people of our countries - through which flow admiration and affection, co-operation and opportunity - strengthening and enriching us all'.
Barbados is following other Caribbean nations who have also dispensed with the Queen as their head of state, with Guyana becoming a republic in 1970, Trinidad and Tobago following in 1976 and Dominica two years later.
In recent years Jamaica has also flagged it wants an elected head of state, with Prime Minister Andrew Holness saying it is a priority of his government, but has yet to achieve it.
Charles is also expected to talk about reaffirming the friendship he has had with the island since he first visited 50 years ago and praise the invaluable contribution of the Barbadian diaspora in the UK.
During the ceremony, service personnel will march past the prince and give their final salute to the monarchy before the Queen's standard is lowered and the presidential flag raised.
Celebrations got underway the Barbados's capital Bridgetown ahead of the ceremony swearing in its first president
Demonstrations are expected during the day with some Bajans demanding an apology and reparations from the monarchy and UK Government for slavery.
Charles will also receive the Freedom of Barbados, awarded for extraordinary service to the country, the Caribbean diaspora or to humanity at large.
The Queen has been Barbados's head of state since it became independent in 1966 but the issue of becoming a republic has been discussed at national level during the following decades.
Barbados is one of the Queen's 16 realms - countries where she is head of state - and in the Caribbean region other countries include Antigua and Barbuda, Bahamas, Belize, Grenada, Jamaica, Saint Kitts and Nevis, Saint Lucia and St Vincent.
Charles arrived in Barbados on the ministerial jet Voyager late on Sunday night local time, and was greeted by a large diplomatic party led by Britain's high commissioner to Barbados Scott Furssedonn-Wood.
Barbadian prime minister Mia Motley and military chiefs lined a red carpet and were introduced to the prince.
Also part of the welcoming group was a Guard of Honour and military band, and a deafening 21-gun salute rang out across the Grantley Adams