It is centred in Barbados, whose Prime Minister, Freundel Stuart, announced last year that the island would drop the monarchy and elect a president to coincide with the anniversary celebrations on November 30, but since then the plan has been quietly postponed, to the annoyance of many citizens.
Instead of a president they will have to make do with an appearance by the "Queen of Barbados", the singer Rihanna, at a concert attended by Prince Harry.
The Not My Prince movement has even quoted the words of the Prince's girlfriend Meghan Markle for its own ends. Miss Markle, who has a black mother and a white father, proudly talks about her ancestors who were slaves, and said in one interview: "You create the identity you want for yourself, just as my ancestors did when they were given their freedom."
There are, however, plenty of Prince Harry fans ready to give him a warm welcome.
Antigua and Barbuda has created a special cocktail in his honour, called, appropriately, The Prince's Ginger, using the country's English Harbour Rum, with pineapple slices, lemon and pineapple juice. It was inspired by a liqueur created for King Edward VII in 1903 called The King's Ginger, which the king liked to sip during morning carriage rides.
Prince Harry is in the Caribbean at the personal request of the Queen.
Barbados and Guyana each invited the Queen to be the guest of honour at their respective 50th anniversary celebrations, while Antigua and Barbuda is celebrating the 35th anniversary of its independence.
Because the Queen no longer undertakes long-haul travel, she asked Prince Harry to go in her place. The diplomatic importance of his mission will be drilled into him daily by Sir David Manning, his adviser on foreign affairs and the former ambassador to the US. He will never be more than a few paces away from the Prince throughout the trip.
The Prince's sea legs will be tested to the limit during the trip, as he will be ferried between islands and will sleep aboard the Royal Fleet Auxiliary Wave Knight, a tanker used for refuelling Royal Navy vessels in the area.
The tour will include a 20-hour voyage between St Vincent and the Grenadines and Grenada next weekend.
The Prince will travel with a staff of 10, comprising his private secretary Edward Lane Fox, Sir David Manning, four press officers, two programme co-ordinators, a visit support officer and an orderly, who will all travel with him aboard the Wave Knight.