The British Commonwealth of Nations was the result of the 1926 Balfour Declaration which stipulated that the relationship between Britain and her Dominions was equal in status. This stipulation was formalized officially in Section 4 of the Statute of Westminster in 1931. It stated: 'No Act of Parliament of the United Kingdom passed after the commencement of this Act shall extend, or be deemed to extend, to a Dominion as part of the law of that Dominion, unless it is expressly declared in that Act that that Dominion has requested, and consented to, the enactment thereof.' In section 1, 'Dominions' were specified as: 'the Dominion of Canada, the Commonwealth of Australia, the Dominion of New Zealand, the Union of South Africa, the Irish Free State and Newfoundland'. The main effect of the Statute was the establishment of legislative equality between these dominions and the United Kingdom.

Concerning the status of Great Britain and the Dominions, the Balfour Declaration stipulated: 'They are autonomous communities within the British empire, equal in status, in no way subordinate to one another in any aspect of their domestic or external affairs, though united by a common allegiance to the Crown, and freely associated as members of the British Commonwealth of Nations.' The Balfour Declaration was one of the outcomes of the 1926 Imperial Conference in London. Section III concerns the special position of India: 'It will be noted that in the previous paragraphs we have made no mention of India. Our reason for limiting their scope to Great Britain and the Dominions is that the position of India in the Empire is already defined by the Government of India Act, 1919. We would, nevertheless, recall that by Resolution IX of the Imperial War Conference, 1917, due recognition was given to the important position held by India in the British Commonwealth. Where, in this Report, we have had occasion to consider the position of India, we have made particular reference to it.' India was included in the proposed Sub-Conference on Merchant Shipping Legislation. As a result of the Declaration, four basic characteristics of members of the Commonwealth were agreed: these were equality of status, autonomy in internal and external affairs, common allegiance to the Crown and the free association of the member states in the Commonwealth. Many of the recommendations of the Balfour Declaration became law in 1931.

Meanwhile, however, in the period between the Declaration of 1926 and the Statute of Westminster of 1931, British-Indian relations worsened, culminating in the failure of the Round Table Conferences (1930-1932). The Indian National Congress fought for Dominion status for India, the Simon Commission was boycotted and Gandhi launched a major civil disobedience movement. The strained Anglo-Indian relationship in this period left India out of the Statute of Westminster, 1931, and without Dominion status.

The London Declaration of 1949 ended the British Commonwealth of Nations. In order to accommodate constitutional changes in India, the members of the British Commonwealth of Nations declared: 'The Governments of the United Kingdom, Canada, Australia, New Zealand, South Africa, India, Pakistan and Ceylon, whose countries are united as members of the British Commonwealth of Nations and owe a common allegiance to the Crown, which is also the symbol of their free association, have considered the impending constitutional changes in India.

'The Government of India have informed the other Governments of the Commonwealth of the intention of the Indian people that under the new constitution which is about to be adopted India shall become a sovereign independent republic. The Government of India have however declared and affirmed India's desire to continue her full membership of the Commonwealth of Nations and her acceptance of The King as the symbol of the free association of its independent member nations and as such the Head of the Commonwealth. [...] Accordingly the United Kingdom, Canada, Australia, New Zealand, South Africa, India, Pakistan and Ceylon hereby declare that they remain united as free and equal members of the Commonwealth of Nations, freely co-operating in pursuit of peace, liberty, and progress.'

Thus, with the London Declaration, the British Commonwealth of Nations officially ended and became the Commonwealth of Nations.