By diplomatic correspondent James Robbins

When the British Airways flight carrying Iran's Foreign Minister, Dr Kamal Kharrazi, touched down at London Heathrow Airport just before midday on Monday, over 20 years without such direct contact was ended.

Most British diplomats hadn't even joined the Foreign Office the last time an Iranian minister was invited to London. The freeze on relations stretches way back to the 1970s, before the Islamic revolution, when Ayatollah Khomeini's followers overthrew the Shah. So Monday's handshake between Tony Blair and Iran's foreign minister was an important symbol.

Nudging politics towards reform

Kamal Kharrazi represents the reformists in Iran. It was he who gave assurances the Iranian government would no longer pursue the fatwa, or death sentence, against Salman Rushdie.

It was only when Dr Kharrazi announced in 1998 that the Iranian government was withdrawing all support for anyone who planned to kill the author of The Satanic Verses that the road to new relations with Britain was opened.

Dr Kharrazi is one of those in Iran trying to nudge politics and society away from the grip of fundamentalist clerics who still have the ultimate hold on power. Britain hopes this visit will strengthen the forces of change.

In turn, Kamal Kharrazi needs to show positive results to strengthen his hand against the arch-conservatives at home opposed to any engagement with the west.

Lingering mistrust of Israel

There were no astounding breakthroughs in the hours of close discussion on a huge range of subjects between the Foreign Secretary, Robin Cook and his Iranian visitor but then neither side really expected that.

The Foreign Office is content that Iran is apparently more receptive to co-operation with Britain over government guarantees for exporters visa requirements and joint action to try to choke drug supplies from Afghanistan through Iran to the West.

Dr Kharrazi apparently impressed many of the MPs he met by taking a less hostile approach to Israel and the Middle East peace process. Although he made clear he and his government still didn't believe Israel was capable of reaching a genuine agreement with the Palestinians guaranteeing the rights of all refugees.

Robin cook stressed the British view that detainees in Iran, including 13 Iranian Jews accused of spying, must be given a fair and open trial as part of a general improvement in human rights.

Protesters target Iranian minister

Kamal Kharrazi's schedule in London was dogged by protesters on Monday. Groups opposed to the Iranian regime protested outside the talks and paint-filled eggs were thrown at the Iranian minister's car.

He spent much of the rest of his visit trying to persuade Britain his country really is on a new, democratic track. Kamal Kharrazi avoided open criticism of the Muslim clerics with whom his government must share power but he said he was confident the reformers would be stronger after next month's parliamentary elections.

The British government is convinced it is right to encourage the process with closer links, so Robin Cook and Kamal Kharrazi signed an agreement committing both sides to open up more trade, as well as scientific and academic exchanges.

More solid British aid includes a thousand suits of body armour already given to Iranian anti drug squads. They have taken heavy losses fighting gun battles with gangs smuggling heroin from Afghanistan, much of it for the British market.

Commitment on both sides

But the greatest importance of this visit has been political.

Britain has taken a direction entirely at odds with the United States which still brands Iran a state supporting terrorism.

Although Dr Kharrazi did not disguise his complete mistrust of Israel, and his pessimism about the peace process - he did suggest closer links between Iran and Europe would reduce the deep suspicion of the West among his fellow Iranians. He hoped the Americans might eventually shift, seeing their allies move.

Robin Cook will go to Teheran in the spring, a quick return visit to demonstrate a new commitment on both sides.