The British Empire became the largest in human history, reaching its peak of expansion in 1922 covering 25% of the world's land surface, 20% of global population, and all major commercial routes by sea, but began to disintegrate after WW2 as the US and Soviet Union emerged as superpowers. Moreover, from the 19th century, the UK began to allow its colonies to have big autonomy, especially where the population was mainly White.
This was the case of Canada, that in 1867 became the "first independent state within the British Empire", with Australia and New Zealand following the same path just some decades after. Besides the fact that ideas about freedom and equality among nations became dominant at the time when the United Nations was founded in 1946, at home, the UK was bankrupt and left-wing governments, which favored decolonization, often held power in London and pushed to end the empire rule.
But, in order to maintain British influence around the world during these geopolitical changes, the Crown pushed for the creation of a modern Commonwealth of Nations in 1949 with countries that were former UK colonies. It was established that its members "shall be free and equal, in no way subordinate to one member, although accepting the British monarch as the head of the organization".
The Commonwealth differs from other international organizations like the European Union or United Nations as it has no formal constitution or bylaws. Instead, the countries are held together voluntarily with the purpose of "seeking world peace, liberty, human rights, equality, free trade, and accepting the English as official language to make international agreements". Basically, the Commonwealth of Nations serves mostly as a 'networking group' that helps each country to strengthen its political status and increase economic ties with the rest by having favorable trade deals.
The Commonwealth of Nations has been a natural continuation of the British Empire, but the allegiance to the Crown was removed initially to allow the new independent republic of India to stay as a member. Indeed, the post of leading the organization is largely ceremonial and non-hereditary, although each country of the Commonwealth had agreed that King Charles III, the son of former Queen Elizabeth II, should take over this position.
Currently, the Commonwealth of Nations is composed by 56 countries that are mostly former British colonies, although this is not a requirement to become a member anymore, as other countries with other colonial rule as Mozambique (Portugal), Rwanda (Germany and Belgium), Togo and Gabon (France) became part of it in the last 30 years. Meanwhile, other former British colonies like Egypt and Ireland, quickly rejected the membership because of strong anti-monarchist and nationalist sentiments there.
This group of countries is home to 2.5 billion people, a third of the world’s population, and represents the fourth-largest political bloc in terms of economic size after the US, China and the European Union. Imports and exports with the Commonwealth accounts currently for 10% of the UK's total trade compared to 50% with the EU, 20% with the US, and 10% with China; and the UK was the largest economy in the Commonwealth until India surpassed it clearly in 2021. Other countries, like Australia, Canada, Nigeria and Singapore, contribute to the economic dynamism of the bloc and their rapid growth could benefit the UK economy in the medium term.
The most representative feature of this union by 'british values' is the Commonwealth Games, a multi-sport international competition that is held every four years in one of the member countries. Moreover, the states have promised to oppose "all forms of discrimination, whether rooted in gender, race, color, creed, political belief or other grounds". When this was not respected, the membership was suspended; that was the case with the Apartheid policies of South Africa (1961-1994), dictatorship in Pakistan (1972-1989), Gambia (2013-2018), Fiji (three times since 1987), and Zimbabwe since 2003.
On the other hand, the British monarch, now King Charles III, is the head of state in 15 of these 56 countries, forming what is called the "Commonwealth of realms". This includes, among others, Australia, Belize, Canada, Jamaica, New Zealand and the Solomon Islands.
Each country of the realm decides how much power it wants to give to the British monarchy, but Queen Elizabeth had constitutional duties in all these countries such as the approval of new governments, some broad legislation, and the grant of state honors or the appointment of certain officials. An extreme case about the use of such powers came in 1973, when the Queen's representative in Australia, Sir John Kerr, unilaterally dismissed the sitting Prime Minister, Gough Whitlam of the Labour Party, to break a parliamentary deadlock. Following that, he appointed the opposition leader, Malcolm Fraser, of the Liberal Party, to succeed him, causing what has been described as the greatest constitutional crisis in the history of Australia.
More recently, the Caribbean island of Barbados left the realm in 2021 , arguing that “the time has come fully to leave the colonial past behind”. Other island countries like Jamaica could follow this example because it has been on their agenda to petition the UK for reparations for the Crown’s role in the transatlantic slave trade.
In the end, the immense popularity of around 70% that the Queen enjoyed at home and overseas was a binding factor in keeping both Commonwealths alive, despite the subordination to the Crown that is associated with racism and colonial rule. But the situation is more uncertain with the new King Charles, as he became quite unpopular following the death of his wife Lady Diana, and because he is more prone to make politically incorrect statements, which normally do not fit well in organizations such as the Commonwealth.