Sikhs take part in a memorial prayer to mark the 33rd anniversary of Operation Blue Star, at the premises of Golden Temple in Amritsar, India June 6, 2017. ( MUNISH SHARMA/Reuters/PA Images )

The Indian army's attack on the Sikh faith's holiest site in June of 1984 killed up to 8,000 people, most of them pilgrims, according to eyewitnesses. The massacre at the "Golden Temple" in Amritsar, Punjab – which was in the hands of Sikh dissidents led by Jarnail Singh Bhindranwale – was among the darkest days in modern India. It marked the start of a wider crackdown that lasted for the next decade, as an armed campaign for an independent Sikh state was crushed by extra-judicial killings and police infiltration.

Human Rights Watch summed up the period like this:

"From 1984 to 1995 the Indian government ordered counter-insurgency operations that led to the arbitrary detention, torture, extrajudicial execution and enforced disappearance of thousands of Sikhs… To hide the evidence of their crimes, security forces secretly disposed of the bodies, usually by cremating them."

The first murky chapter of this period had barely closed when, in 1985, a British Army major wrote a letter arguing strongly in favour of providing India with a training film about riot control chemicals – possibly tear gas – in order to win arms deals.

In the letter he complained that a colleague was being "unduly defensive on the subject of riot control agents… furthermore, with an eye on defence sales, we believe that India provides significant potential for sales of equipment. If the UK does not provide such assistance and equipment other nations will!"

The major added that, the previous year, an Indian general had already received a confidential briefing from British soldiers about gear used to crush domestic unrest: "In this respect you should be aware that last year [1984] the CGS [Chief of the General Staff] of the Indian Army received a brief at Confidential level on IS [Internal Security] and COIN [counter-insurgency] equipment."

The letter is a snapshot of Britain's involvement in Indian affairs at the time, revealed today by VICE, as the Foreign Office releases its records from 1985 to the National Archives. Significantly, VICE has found that almost a third of its Indian files are being kept secret, over three decades after they were written. Parliament's Sikh MPs said that this is a "cover-up" and called for an independent inquiry.

The letter from a British major advocating selling arms to India in 1985 (Photo by Phil Miller)

The 47 hidden files – alluded to in a National Archive spreadsheet but kept from the public – include one about India's National Security Guard, a commando unit that led two subsequent raids on the Golden Temple, the Sikh holy site in Amritsar. This unit, known as the Black Cats, is suspected of receiving SAS training. Files on arms sales are also being kept secret.

One file that was released shows the British army gave India's top brass a briefing on counter-insurgency and internal security equipment in 1984, which the MOD hoped would boost arms sales. This revelation will put pressure on ministers to open a new inquiry into the episode.

CAMERON'S WHITEWASH

In 2014, I found letters revealing that Margaret Thatcher sent an SAS officer to India months before the Golden Temple massacre, to advise local forces on how to plan the operation. It was buried among hundreds of telegrams about attempts to sell British weapons and helicopters to India, in a bid to make money and seduce Delhi away from Soviet benefactors.

The revelation caused outcry in Britain and India, forcing then-Prime Minister David Cameron to order a review by the government's top civil servant, Sir Jeremy Heywood. Heywood's report, released just weeks later, downplayed the SAS role, claiming it had "limited impact in practice" and was not motivated by arms deals worth £1 billion.

The new files revealed by VICE are enough to show that British military advice for India went much further than Heywood claimed. They reveal that, in 1984, the UK gave a confidential briefing on internal security and counter-insurgency equipment to the Indian Army's Chief of the General Staff, one of its highest-ranking military officers. The British military believed that the briefing helped persuade India to buy UK arms and secure an advantage over competitors.

Preet Kaur Gill, the first female Sikh MP and chair of the All Party Parliamentary Group for British Sikhs, said: "Clearly this would suggest that the Heywood review was a whitewash – he had access to these files but failed to mention that Britain briefed India's top brass on counter-insurgency."

THE SAS AND THE BLACK CATS

VICE can also reveal new evidence suggesting British forces may also have helped India set up a controversial special forces unit. India's National Security Guard, known as the Black Cats, was formed immediately after the Amritsar massacre. It is an elite counter-terrorism squad that wears a distinctive all black commando uniform with a cat insignia.

Concerns that the SAS may have trained the Black Cats surfaced last year, after I found documents showing the British government considered giving them SAS training in the immediate aftermath of the Golden Temple massacre. A letter written just weeks after the deadly raid said Whitehall received "an Indian request for military assistance in the setting up of a National Guard for internal security duties", to which the FCO's counter-terrorism team was asked to "comment on the possibility of an SAS involvement".

Another concern was that an entire file dedicated to India's National Security Guard, dated 1984, was kept under lock and key. The Foreign Office refused to clarify if the SAS became involved, despite Sikh activists highlighting that the Black Cats led two further attacks on the Golden Temple in 1986 and 1988. When the Heywood review was published, then-Foreign Secretary William Hague had told Parliament there was no evidence of British military involvement in these later raids.

However, VICE can today reveal that the Foreign Office has a file on the Black Cats from 1985 as well as 1984, and that both are being kept secret. It is highly unusual for the government to keep files on specific foreign military units, and its existence will add to suspicions that the SAS was involved in training them.

Preet Kaur Gill MP said: "The government's refusal to release so many records from 1985, including another file about India's National Security Guard, is a huge cover-up. It will cause a backlash from Britain's Sikh community who need to know if the SAS trained this unit."

Tanmanjeet Singh Dhesi, Parliament's only other Sikh MP, said: "It is absolutely ridiculous that our government is still trying to cover up what happened three decades ago. We should have full disclosure so the public can make up their own minds about what happened. The new revelations highlight what many of us have said about the Heywood Review for years – the Tory government is brushing things under the carpet. Justice needs to be delivered for those countless individuals who have suffered such great loss."

The MPs, who are both Labour, pointed towards their party's 2017 manifesto, which calls for "an independent inquiry into Britain's military role in the 1984 raid on the Golden Temple in Amritsar".

Gill added that her cross-party group for British Sikhs would also "strongly consider this latest development".

A spokesperson for the Foreign Office said, "Redactions in these files have been made on the same legal basis as all other Foreign Office files which are reviewed. Overall we only redact around 1 percent of content across all historic files that we review. We will review any information that has not been released again at a later date and would consider any individual requests for the information under the Freedom of Information Act. The question of UK military assistance was dealt with in the 2014 review by the Cabinet Secretary."