Damien Grammaticus: "Letter will not influence General Pinochet's situation"

Even before the former Chilean dictator offered his country's tacit support to the UK during the 1982 Falklands War, Margaret Thatcher had long been an admirer of his radical free market economic policies.

General Pinochet was detained in London on 17 October following a request for his arrest and extradition by two Spanish judges investigating some of the 4,000-plus political murders believed to have been committed during his 1973-1990 rule.

General Pinochet: Free market pioneer

Baroness Thatcher demanded his immediate release in a letter to the Times newspaper on Thursday.

In her letter, Baroness Thatcher wrote: "By his actions the [Falklands] war was shortened and many British lives were saved."

It is understood that while Chile did not express open support for the UK during the conflict, it did provide material assistance, most notably in allowing the SAS to set up a base on Chilean soil.

Baroness Thatcher: General Pinochet made a great impact

But it is General Pinochet's adoption of the ideas expressed by the American economist Milton Friedman that is believed to have had the greatest impact on Baroness Thatcher.

The general seized power in 1973 from the Marxist government of Salvador Allende and immediately overturned its state controls in favour of a programme of sweeping privatisations in accordance with Friedman's free market thinking.

It won Baroness Thatcher's admiration and, to some extent emulation in the reforms she brought in as prime minister.

Despite this, she has always been acutely aware of General Pinochet's extremely poor human rights record - alluding in her letter to abuses "on both sides of the political divide" - and kept her distance while in office.

The Thatchers entertained General Pinochet at their home

Following her resignation, however, she allowed more open social contact and even planned to attend a private function with the former dictator during her speaking tour of South America in 1994. She was forced to cancel through illness.

General Pinochet, a confirmed anglophile who once described the UK as "the ideal place to live", reciprocated with equal admiration for Baroness Thatcher.

He reportedly made a habit of sending chocolates and flowers to her during his twice-yearly visits to London and took tea with her whenever possible.

Just two weeks before his arrest, General Pinochet was entertained by the Thatchers at their Chester Square address in London.

The Thatchers survey war graves in the Falklands

It was perhaps the final straw that Baroness Thatcher's mentor and ally has been detained at a time when Argentina's President Carlos Menem will be visiting the UK to "build bridges" 16 years after the two countries went to war over the Falkland islands.

"It would be disgraceful to preach reconciliation with one, while maintaining under arrest someone who, during that same conflict, did so much to save British lives," she wrote.