I have behind me not only the splendid traditions and the annals of more than a thousand years but the living strength and majesty of the Commonwealth and Empire; of societies old and new; of lands and races different in history and origins but all, by God's Will, united in spirit and in aim.

About 2.5 billion people - out of a global population of eight billion - live in the 56 Commonwealth countries.  The Commonwealth also makes up a quarter of the world's land mass. The biggest country by population is India, which accounts for about half of the total. Pakistan, Nigeria and Bangladesh are the next biggest countries by population, with the UK fifth. Some of these countries were previously in the British Empire, some are still British dominions, while others had no colonial links to Britain but have chosen to join the global association. 

15 Member States have King Charles III as Head of State,  Five countries - Lesotho, Eswatini (previously known as Swaziland), Brunei Darussalam, Malaysia and Tonga - have their own monarch,  and 36 nations are republics.

Some Member States were never members of the British Empire. Rwanda and Mozambique in Africa, became members in 2009 and 1995 respectively, although neither were colonised by Britain, Rwanda which had its own regnant King, until 1962, was previously under the administration (until 1918) of Germany and, until independence, Belgium. 

The Commonwealth has also lost some members over the years. South Africa withdrew in 1961 after it was criticised by Commonwealth members for its apartheid policies. It became a member again in 1994. Pakistan was ejected after a military coup in 1999, but was readmitted in 2004. Membership was suspended again between 2007 and 2008. Former president of Zimbabwe, Robert Mugabe, took his country out in 2003 after its membership was suspended amid reports of election rigging. It applied for re-admission in 2018, but no decision has been reached. The last country to leave was the Maldives in 2016, but it re-joined in 2020.

The modern Commonwealth was formed in 1949, after "British" was dropped from the name and allegiance to the Crown was removed. 

Three people have been head of the Commonwealth- King George VI, Queen Elizabeth II and King Charles III.   It's not a hereditary role, although the Commonwealth accepted King Charles as its head in 2018, when he was Prince of Wales.