David Snoxell is Co-ordinator of the Chagos Islands (BIOT) All-Party Parliamentary Group.

Before Mauritian independence in 1968, the UK detached the Chagos Archipelago in 1965 to create a new colony, the British Indian Ocean Territory (BIOT), for the construction of a US military base on the largest island, Diego Garcia.

The UK promised to return the territory to Mauritius when no longer required. In 1979 Margaret Thatcher told Parliament that sovereignty would “revert” to Mauritius when the islands were no longer needed for defence purposes. That commitment has been repeated by successive governments.

In 1968-73 the Chagos Islanders were deported to Mauritius and Seychelles, although they could have remained on the 54 “Outer Islands” which have never been required for defence facilities.

It is 45 years since the last of the Chagossians living in the British Indian Ocean Territory were deported, 42 years since the issue was first raised in Parliament, 20 years since the most recent litigation began, 18 years since the High Court re-instated the right of abode, 14 years since the Foreign Secretary used the Royal Prerogative to overrule that decision and 10 years since the Chagos Islands (BIOT) All-Party Parliamentary Group was established.

Since my last piece in ConservativeHome in December 2017 a resolution of the UN General Assembly in June 2017 referred the issue of decolonisation and Chagossian resettlement to the International Court of Justice (ICJ). I have been dealing with Chagos since 1995 and never expected it to reach the ICJ. I attended the hearings in The Hague, 3-6 September.

The Mauritian team, led by Sir Anerood Jugnuath QC, PC, former Prime Minister and President, supported by Philippe Sands QC, spoke with passion and vigour, the UK team led by Robert Buckland QC, the Solicitor General, with detached forensic analysis.

But how could the UK team do otherwise? Their unenviable task was to defend the UK’s conduct of 53 years, which continues to violate the human rights of the Chagossians and avoid a diplomatic resolution of the sovereignty question.

Mauritius and the UK were each allocated three hours on the first day; 22 states then made oral submissions followed by the African Union, representing 55 member states. The UK was supported by the US, Israel, and Australia, and on the jurisdictional point by Germany. All other states supported Mauritius. The UK and its supporters argued from technical legal grounds, leaving Mauritius and the Chagossians occupying the ethical high ground.

A Chagossian contingent was part of the Mauritian delegation. None spoke but the Court was shown a moving video of Marie Liseby Elisé, who was present, describing her experience of being deported from Peros Banhos (Outer Islands) in 1973 and the death of her baby as a result. Both the UK and US expressed sympathy with the Chagossians, the US referring to their “sufferings” and the UK to their “shameful and wrong treatment”.

As the new Attorney General, Geoffrey Cox QC, has been a member of the APPG since 2008 and Standing Counsel for Mauritius, the UK was represented by the Solicitor General. The UK arguments were predicated on four assertions: no legal right to self-determination existed in 1965 or in 1968; the people of Mauritius had repeatedly consented to detachment (“freely expressed will of the people” in UN language); territorial integrity did not exist as a concept for non-self governing territories at that time; and the Mauritian authorities were not put under duress to agree to detachment. These historical arguments were strongly contested by Mauritius and her allies.

It was unfortunate that in addressing the Court, one UK lawyer noted that it was being asked to form an Opinion “in the absence of the witnesses to the key meetings, as they have long since died”. He was standing near the only surviving politician who was at the 1965 Lancaster House Constitutional Conference, a point Sir Anerood had made in his opening address.

The UK proposition that the people gave their consent is preposterous. In 1965 few Mauritians knew about the Chagos Archipelago. There was no referendum or plebiscite and Chagossians were neither consulted nor consented. The 1967 Mauritian general election was about forthcoming independence and economic issues. And yet the UK legal team claimed that “The UK sought and obtained consent in multiple steps, with time for reflection and consultation by the people of Mauritius and their representatives”.

On duress the UK cited several comments by Sir Seewoosagar Ramgoolam, the then Chief Minister, in support of its claim. No mention was made of what he later told the 1982 Select Committee of the National Assembly that the prime reason he had accepted the excision was that he felt “he had no legal instrument to prohibit the UK Government from exercising the powers conferred upon it by the Colonial Boundaries Act 1895, which powers could not be resisted even by India when the partition of that country took place before its independence.”

The Court could decide that it does not have jurisdiction to give an Advisory Opinion. If it gives one I would expect the APPG to mount pressure in Parliament to ensure that the Government respects it. As a founding member of the ICJ and strong advocate of the rule of international law it is unlikely that the UK would ignore an Advisory Opinion.

A decision is expected before the end of March 2019. Whatever the legal outcome the profile of Chagos and the Chagossians has been raised to the international level and is back on the UN agenda after 52 years. At its 70th meeting on 10 October the APPG agreed proposals for breaking the political impasse which it hoped the Foreign Office would consider in anticipation of an Advisory Opinion.

A judicial review of the Government’s decision in November 2016 not to restore the right of abode and allow resettlement is being heard in the High Court, commencing 10 December. This will be the seventh case which Governments have contested since 1999. Had they stood by Robin Cook’s decision in 2000 to accept the High Court judgment much of this costly litigation could have been avoided.

At a time when the UK’s standing and future in the world is uncertain an ICJ Opinion offers a diplomatic way forward with the potential for compromise and negotiation.