While he was under house arrest in Surrey in 1999, the former Chilean military dictator Augusto Pinochet received a fine malt from an old friend.

“Scotch is one British institution that will never let you down,” read the accompanying note from its sender: the former British prime minister Margaret Thatcher.

The detail, revealed this week in the third volume of Charles Moore’s biography of Baroness Thatcher, adds further colour to the close relationship between Thatcher and the man responsible for the death of more than 2,000 people and the torture of many more.

Thatcher was appalled that the Labour government had allowed the arrest of Pinochet while he was in London for medical treatment, overriding his diplomatic immunity.

“I don’t know when or how this tragedy will end,” Thatcher told the 1999 Conservative party conference to warm applause, “but we will fight on for as long as it takes to see Senator Pinochet returned safely to his own country. The British people still believe in loyalty to their friends.”

Although they never met in power, Thatcher was impressed by the success of Chile’s neoliberal economic program and Pinochet’s bloody stance against communism in Latin America.

Above all she felt a “great debt for [Pinochet’s] secret actions during the Falklands war”, according to Moore.

During the conflict, Pinochet installed a military radar in southern Chile to update British intelligence on the movements of Argentina’s air force. He also provided safe passage for SAS troops following a botched reconnaissance mission on mainland Argentina.

But for survivors of Chile’s dictatorship, the relationship between the two leaders is still cause for anger.

“For a British authority figure to publicly support the most bloody dictator in Latin America violated the memory of the thousands of Chileans who were killed, imprisoned and tortured under the dictatorship” said Alicia Lira, the president of the Association for Relatives of the Executed.

“Her words were an offense to the Chilean people.”

According to Chile’s truth and reconciliation commission, 2,279 people were murdered by Pinochet’s military regime, and a further 27,255 were tortured between 1973 and 1990.

Thanks to public pressure from figures such as Lira, whose husband was killed by the military in 1982, former members of the regime continue to stand trial. On Wednesday, Chilean courts sentenced one of Pinochet’s former bodyguards, Cristián Labbé, to three years in prison for the 1973 torture of a political prisoner.

Pinochet’s taste in tipples was for years kept under wraps by US secret services.

When an uncensored version of a Defense Intelligence Agency profile of the dictator was released under pressure from the National Security Archive at George Washington University, one of the details previously deemed too sensitive to release was : “Drinks scotch and pisco sours; smokes cigarettes; likes parties.”

After the return to democracy however, Pinochet retained the support of many rightwing Chileans. In response to his arrest in the UK, a group of conservative senators demanded a boycott of British goods – including whisky.