THATCHER'S government was "intimately aware" of atrocities committed by Robert Mugabe's army – but was "wilfully blind" to thousands of deaths, research claims.

Between 10,000 and 20,000 people are thought to have died during a brutal nine-month clampdown on dissidents in the newly-independent Zimbabwe of 1983.

The Fifth Brigade, a division of the Zimbabwean National Army including soldiers trained by the UK's Ministry of Defence, committed mass killings, torture and rape against thousands of the Ndebele people said to be dissidents or affiliates of the opposition ZAPU party (Zimbabwean African People’s Union).

Some were burned alive during the "Gukurahundi" massacres, with up to 5,000 unarmed civilians dead within the first six weeks alone.

Soldiers of the Fifth Brigade were said to have been ordered to "kill anything that was human".

According to newly-released documents uncovered by Dr Hazel Cameron of St Andrews University, British officials in the country knew what was going on and helped to cover up the carnage.

Cameron claims her self-funded work proves these UK Government workers were “consistent in their efforts to minimise the magnitude” of the state-sanctioned murders and took part in a "conspiracy of silence".

The previously unseen material implicates Margaret Thatcher’s Tory Government and Robin Byatt, the British High Commissioner in Harare, for their “wilful blindness” during the period of violence.

Rather than saving Ndebele lives in the Matabeleland area, senior Westminster figures are instead said to have concentrated on the reputations of their own armed forces, with race a major consideration.

The papers show black civilians were of less concern to the British than their white counterparts.

Cameron, a lecturer in International Relations, said: "It is quite clear from these documents that one of the major concerns for the British at the time was the reputation of their own army and British public opinion as opposed to the ongoing atrocities and human violations in Matabeleland.

“Instead, the Zimbabweans who were of concern to the British government, and influenced their diplomatic approach, were the many white Zimbabweans living in the affected regions, and who were unaffected by the extreme violence of Fifth Brigade.

“That the British Government chose to adopt a policy of wilful blindness towards the atrocities undoubtedly constituted naked realpolitik. Mugabe himself was said to view the British response favourably, saying ‘you have to hand it to the British, they know how to behave in this kind of situation’.”

Cameron examined 2,600 pages of documents for the study to establish what the US and UK knew. The papers were obtained through Freedom of Information requests and Cameron said she was "astounded" to receive so much uncensored material.

The dataset includes minutes of meetings and other relevant communications between the British High Commission in Harare, the Prime Minister’s Office, the British Foreign and Commonwealth Office, the Cabinet Office and the Ministry of Defence in London, as well as the US Department of State and its embassy.

Declassified documents from the US “demonstrated concern”, but the UK was "determined" to continue good relations with Mugabe for economic reasons.

A cable from Byatt to then-Foreign Secretary Geoffrey Howe refers to Britain’s “important” interests in investment and trade worth a combined £920 million, despite the “occasional Zimbabwean perversity”.

The Foreign Office said: "The UK Government condemns the brutal suppression in Matabeleland in the early 1980s. The British Government has a strong record of supporting human rights and the rule of law in Zimbabwe."

The findings are published in The International History Review.