Image caption Although never a close ally of Margaret Thatcher, he held key positions in her government

Former Conservative cabinet minister Lord Prior has died at the age of 89.

He served as Secretary of State for Northern Ireland during the height of the Troubles in the early 1980s.

Before that, he was Secretary of State for Employment, often disagreeing with then PM Margaret Thatcher on economic matters and industrial relations.

Lord Heseltine said his ex-colleague, who after leaving front-line politics became chair of defence business GEC, had been a "rock of integrity".

Jim Prior, as he was commonly known, was an MP for 28 years - representing the Suffolk constituencies of Lowestoft and Waveney from 1959 to 1987.

The Conservative politician and farmer, who served as agriculture minister under Edward Heath and unsuccessfully stood for the party leadership in 1975, was an important figure in the first Thatcher administration between 1979 and 1983.

He was not an ideological soul mate of the prime minister's, disagreeing with many of her economic policies and seeking a more conciliatory relationship with the trade unions.

'One Nation Conservative'

He was one of the so-called "wets" in her first cabinet generally hostile to proposed spending and tax cuts put forward by the PM and her Chancellor Geoffrey Howe.

Instead, he was in favour of increased spending to boost jobs at a time when unemployment levels were rising sharply, topping more than three million in early 1982.

Image copyright Getty Images Image caption He stood for the Conservative leadership in 1975 but only got 19 votes

Image caption But he went on to to become a key figure in the economic battles of the early 1980s

Image copyright PA Image caption He also had to respond to an escalation of IRA attacks on the mainland

By that point, Lord Prior had been moved to Northern Ireland in a reshuffle in September 1981, in which a number of leading wets were either sacked or demoted.

He served in Northern Ireland for three years between 1981 and 1984 - a period in office marked by a number of high-profile IRA attacks in Northern Ireland and the mainland - including the 1982 Hyde Park bombing and the 1983 attack outside Harrods.

'Sense of service'

Paying tribute to Lord Prior, his former colleague Lord Heseltine said he had been a "one-nation Conservative" with strong values and a profound "sense of service".

"He knew what he believed in and no-one was going to shift him," he said.

Image caption Lord Prior said he was playing for "high stakes" in opposing Margaret Thatcher and lost

"He wasn't really a politician, I don't think, curiously enough, although you have to be very well-versed in political skills to hold that Northern Irish job.

"But I think of him much more as someone who's in politics because he had a sense of service, a sense of obligation."

And former Education Secretary Lord Baker said that while he had had his disagreements with Margaret Thatcher, he had remained the "epitome of decency" at a "very difficult" time.

"He was dealing with militant trade unionism," he told the BBC News channel.

"The trade unions had actually brought Ted Heath down and James Callaghan down and Margaret Thatcher was quite determined that she wasn't going to be the third victim.

"Jim Prior struggled very hard at that time to find a way through that would somehow reconcile the interests of organised labour with those of safely continuing government. That was a very difficult thing to do."

Lord Prior resigned from the Cabinet in 1984 and, after leaving the Commons, later sat in the House of Lords for nearly 30 years.

His son David was a Conservative MP between 1997 and 2001 who also later joined the Lords. He is currently a junior health minister.