Margaret Thatcher's Foreign Secretary wanted the Metropolitan Police to ban protests in order to protect trade deals. Secret documents revealed for the first time by VICE after a four year freedom of information battle show how Sir Geoffrey Howe wanted to stop Sikh activists from demonstrating in London, fearing they would scupper arms deals and other business with India worth £5 billion.

The documents relate to secret discussions that happened in 1984, in the weeks after Indian Prime Minister Indira Gandhi was assassinated by her Sikh bodyguards. Her murder was a reaction to the Indian army's bloody assault earlier that year on the Sikh holy site in Amritsar, which was occupied by disaffected Sikhs. Hundreds, if not thousands, of Sikh pilgrims died in the clearance operation.

The loss of life at Amritsar outraged many Sikhs in the UK, where the community numbered some 350,000. However, Thatcher's Cabinet had a "clear preference… for a ban on Sikh marches". Such action would breach the Public Order Act 1936, which only allowed a ban on freedom of assembly if there was a risk of violence – something the Metropolitan police deemed unlikely.

Despite these legal obstacles, Thatcher's Foreign Secretary argued strongly to consider the wider picture: "Sir Geoffrey Howe continues to believe that a Sikh march in present circumstance would carry very serious risks, both for Indo/British relations and for law and order in this country. Whatever undertakings may be given by the organisers of the march, Sikh extremists are bound to attempt to exploit it."

The Foreign Office was under intense pressure from Indian diplomats to "somehow silence" a leading Sikh dissident in the UK, Dr Chauhan, in ways that the acting Indian High Commissioner "was unable to specify". While the Foreign Office ruled out doing anything illegal, it lobbied the Home Secretary Leon Brittan to ban Sikh rallies in London.

"Such a march would also undoubtedly have serious repercussions in India," Sir Geoffrey Howe's private secretary Leonard Appleyard wrote. "It could help to inflame inter-communal feeling there. It would certainly serve to stir up anti-British feeling, of which there has already been evidence, so putting British property and even lives at risk in India. It will also further intensify the Indian government's resentment against the UK and unwillingness of HMG, as they see it, to do anything to curb the activities of Sikh extremists in this country. Contracts which would be potentially at risk from a trade boycott amount to some £5 billion."

In 1984, Whitehall was eager to sell Westlands helicopters to India's state-owned oil and natural gas corporation, as well as other lucrative arms contracts to the Indian military, involving British companies like BAE.

"Sir Geoffrey appreciates that matters of this kind, arising from events overseas, are probably not directly relevant to the considerations which the Commissioner is entitled to have in mind when considering whether or not to propose a further ban on marches in London," the letter continued. "But he considers that they are illustrative of the extreme tensions which can all too easily arise in London as a result of, or in the course of, any march of the kind proposed… He continues, therefore, to hope that this evidence could enable the Commissioner to continue the ban."

Tensions were running so high that the Foreign Secretary wanted to change the law. The Foreign Office noted, "If the terms of the Public Order Act 1936 do not permit the Home Secretary to implement the clear preference of Cabinet for a ban on Sikh marches, Sir Geoffrey Howe considers that there is a strong case for including within the review of the Public Order Act a serious look at this problem. At first sight, it would seem to be possible to justify to Parliament a discretionary power for the Home Secretary in this area on the grounds of the real dangers that marches can in certain circumstances pose for British interests abroad as well as law and order here.”

Thousands rally in Trafalgar Square in London on June 3, 2018, for the annual remembrance of 1984 Sikh Genocide by the Indian army during "Operation Blue Star" that saw the death of thousands of unarmed Sikh men, women, and children.

Despite these stark warnings, the Home Secretary, Leon Brittan, remained staunchly opposed to such a ban. His private secretary emphasised to the Foreign Office "how much political sensitivity attaches in this country to any curtailment of the right to demonstrate, even though the nature of the demonstration may sometimes be offensive in some quarters".

"Simply to give the Home Secretary a discretionary power to ban marches because of potential damage to our interests overseas as well as law and order here would not, in his view, be an acceptable approach," his aide wrote.

The debate of civil liberties continued well into 1985, when ministers discussed a Sikh demonstration set for Hyde Park in April. The Environment Secretary Patrick Jenkin MP, whose brief included meetings in Hyde Park, said, "The legal opinion we have received is that it would be ultra vires for me to refuse permission solely on the grounds that the Indian government takes a poor view of Sikh demonstrations in this country. There is always the possibility that any decision which I reach, and indeed any conditions I might attach to any permission, could be subject to judicial review."

The papers were kept secret for almost three-and-a-half decades. In 2014, the files were due for release under the "30 year rule", whereby the government makes secret files public after that time period. But when I went to the National Archives to read them, I was told that the Cabinet Office was keeping the documents under lock and key. The only way to gain access was through FOI. I made a request, but the Cabinet Office sat on it, then sent me documents with redactions and kept one file completely secret, saying full disclosure would damage diplomatic relations with India.

I had to take the government to court to gain access to these papers. They spent at least £13,000 of taxpayers' money on lawyers – and that figure was before the lawyers even turned up to the court room. The hearing lasted three days and the government's witnesses gave most of their evidence in secret. A judge ordered Britain’s Cabinet Office to release most of the files, although some parts that relate to the intelligence agencies are still being kept secret.