Image copyright Getty Images

Edward Heath's bitter 25-year feud with Margaret Thatcher, known as "the incredible sulk" is the stuff of political legend.

The BBC has learnt, however, that Baroness Thatcher eventually called her Tory predecessor "one of Britain's greatest prime ministers".

The surprise revelation is contained in Archive Hour: The Heath Enigma on BBC Radio 4, a programme marking the 100th anniversary of Heath's birth.

Margaret Thatcher was Education Secretary in Mr Heath's cabinet between 1970 and 1974. Although never close, they shared a commitment to free market policies.

From 1972, the government began to change course.

A strike by the miners threatened coal supplies to power stations.

War in the Middle East in 1973 led to a sharp rise in oil prices, feeding inflation.

Heath, memories of wartime comradeship still fresh, did not want a confrontation with workers, nor, having grown up during the depression of the 1930s, was he willing to see unemployment rise in order to curb inflation.

Instead, he re-introduced government control of prices and pay.

After the Conservatives lost power in February 1974, Mrs Thatcher was among the senior Tories who concluded Heath's compromises had been a mistake.

The following year she challenged his leadership of the Conservative Party and defeated him.

In a speech delivered in 2000 at a private dinner for fellow veterans of the Heath government, and now broadcast for the first time, Baroness Thatcher says he "showed enormous courage and outstanding qualities of leadership in extraordinarily difficult circumstances".

She hints only in passing at the years of hostility between them, over her anti-inflationary policies as prime minister, her confrontation with the miners, and her very different attitude to Europe: "In the years since, he and I have not always agreed on every political thing, but I was, and I'm proud to have been, a member of his government …"

Archive on 4: The Heath Enigma, 2000 BST Saturday 9 July, on BBC Radio 4 and afterwards on the iPlayer.