Governments usually refuse to capitulate to the demands of terrorists.

And just to make the point, the UK formally pledged not to negotiate with hijackers at the 1963 Tokyo International Convention on Hijacking. But it was a promise that was broken in 1970.

On 6 September that year four airliners were seized by the PLFP - the Popular Front for the Liberation of Palestine, a radical Palestinian faction.

They demanded the release of Fedayeen (members of the Palestinian movement) imprisoned in Germany, Switzerland and Israel.

Dawson's Field: Aircraft destroyed

Two of the planes were taken to a former RAF airstrip in the middle of the Jordanian desert, known as Dawson's Field. A third was blown up in Cairo after the passengers and crew were released.

The fourth hijack failed when both terrorists were overpowered on the plane. One was killed and the other, a woman named Leila Khaled, was arrested. The plane was diverted to Heathrow, the nearest airport.

Khaled, who had been the commando in charge of the operation, was taken into British custody.

Her presence forced the UK into a major international crisis.

Release demands

The PFLP demanded Khaled's release - as well as the other Palestinian extremists. To emphasise the point, a few days later the group hijacked another plane, a BOAC - VC-10 on course from Bombay to Beirut.

The guerrillas now held over 300 hostages, 65 of them British. What should Britain do?

The Cabinet Conclusions from 9 September sum up the dilemma faced by the British Government.

Briefings: Weighed options

"The cabinet faces a difficult and complex decision. A woman named Leila Khaled is being held in the country. Her release is an essential element in the bargain the PFLP leaders are trying to strike."

The PFLP sent a 72-hour ultimatum to the British Government, prompting officials to ponder the pros and cons of releasing her.

"Advantages: We should get her out of our area of responsibility and should be seen to have fulfilled the PFLP demands thereby saving the lives of the United Kingdom Nationals.

"Disadvantages: The pilots and the airlines share the view that there should be no capitulation to blackmail.

"We should also be throwing overboard our previously declared attitude on hijacking and should lose all credibility in international civil aviation circles. We should also be in breach of the Tokyo Convention of 1963."

Thanks to diplomatic work in Amman and the help of an intermediary, the PFLP agreed an extension to the deadline.

Edward Heath's government in London had already concluded that rescuing the hostages was not feasible, and behind the scenes Britain began to negotiate with the hijackers, through both official and its own secret channels.

Cabinet papers: Hussein appeal

The negotiations had some initial success when six days into the crisis, some of the hostages - mostly the women and children - were released unconditionally.

But the hijackers were impatient for results. On 12 September as a warning signal they blew up the three planes.

That act, seen around the world on television, brought home to British officials in Amman the seriousness of the guerrillas' intentions - and the threat to Jordan's King Hussein.

Frantic communications began between the British Ambassador in Amman and London.

"Telex from Amman: Some of the more irresponsible and violent PFLP have got the idea that we are not going to release Leila Khaled.

"They have told us through an intermediary that if we do not within a few hours at least give an assurance that we are prepared to do so something very serious will happen. These people are quite capable of killing hostages."

Escalating violence

The hijackings took place against a background of escalating violence in Jordan as the Fedayeen challenged the government and forces of King Hussein.

Telexes: Embassy fearful

They claimed Hussein had done too little to help them attack Israel after initially providing them with refuge.

With Syria already supporting the Fedayeen cause, the hijack incident was the spark to an already incendiary situation.

Heath agrees release

Prime Minister Edward Heath eventually agreed that Britain had no choice but to go public on its intentions to free Leila Khaled.

At 7pm on 13 September, the BBC World Service broadcast a government announcement in Arabic saying that the UK would swap Khaled for the hostages.

Israel was furious. It believed that the decision would only encourage terrorism. But the documents show that the decision also had ramifications for the stability of King Hussein - and UK-US relations.

Black September

6 Sept: PFLP hijack four airliners, one destroyed, one fails 7 Sept: Fifth hijack. 72-hour ultimatum issued 12 Sept: 255 hostages released, further 56 still held PFLP blow up three jets at Dawson's Field 17 Sept: Fighting between Palestinians and Jordanian forces 19 Sept: Hussein appeals to UK and US 27 Sept: Palestinian-Jordan truce 30 Sept: Leila Khaled released from UK

Within days he had contacted both London and Washington appealing to them for help.

Cabinet papers reveal that at the height of his anxiety, he asked both governments to pass on a plea to Israel to bomb Syrian forces which were poised to intervene on the Fedayeen's side.

This unprecedented appeal - an Arab ruler asking Israel to bomb an Arab neighbour - caused deep consternation in London.

Despite being King Hussein's closest western ally, the British Government agreed not to pass the appeal on to Israel itself and left it in the hands of Washington.

Documents make clear that Washington passed the message to Israel's Prime Minister Golda Meir - but her response remains unknown.

While reports of this behind-the-scenes appeal surfaced at the time, they were vehemently denied by all parties.

Furthermore, in the aftermath of Black September, Palestinians did allege that Israel may have secretly supplied Jordan with arms, accepting the king's view that a Syrian invasion of Jordan could spark a fresh Middle East war.

However, the British Government's decision to negotiate also angered Washington.

'Israel won't lift a bloody finger'

The tensions came to a head in a telephone conversation between Sir Denis Greenhill, the Permanent Under Secretary at the Foreign Office, and Joe Sisco, a senior White House official.

Mr Sisco told Sir Denis: "I think your Government would want to weigh very, very carefully the kind of outcry that would occur in this country against your taking this kind of action.

Documents reveal that Sir Denis replied: "Well they do Joe, but there is also an outcry in this country... your visitor Israel won't lift a bloody finger and put any contribution to a bargain, our people get killed.

"You could imagine how bad that would look and if it all comes out that we could have got our people out but for the obduracy of you and other people so to speak... I mean people say, why the bloody hell didn't you try."

Hostages released

Two weeks later the hostages were safely exchanged for Leila Khaled and six other Palestinian guerrillas held in Switzerland and Germany.

King Hussein: Survived crisis

While the UK chose not to intervene in King Hussein's favour, events on the ground went his way and his military launched a successful campaign against the Palestinians, driving them out of his territory.

Speaking to UK Confidential, Leila Khaled, now a middle-aged housewife, admitted that the PFLP was encouraged by the UK's capitulation to its demands.

"It was a good step for us that we saw governments could be negotiated with. We could impose our demands.

"The success in the tactics of the hijacking and imposing our demands and succeeding in having our demands implemented gave us the courage and the confidence to go ahead with our struggle."

Looking back today, former Prime Minister Edward Heath said that by negotiating with the terrorists he was being pragmatic.

"When you're negotiating with people like that, if you want to achieve your ends, it's very often the better way to do it without a blaze of publicity to begin with.

"We were always realistic, We were very practical about it all."

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