Between Tuesday and Friday the Egyptian and Jordanian security services each sent an agent to London. Two more were due to arrive yesterday and, according to one diplomatic source, MI5 and MI6 were also asking Lebanese intelligence for help.
Mossad, the Israeli intelligence service, had already increased the size of its team in London after warnings that attacks against Israeli and Jewish targets were imminent.
Both Arab and Israeli diplomats claimed that MI5 and MI6 had a 'relaxed' attitude towards the warnings - which came to a peak when the Israeli embassy asked for more protection after 19 July - and an outdated view of Middle East terrorism.
When Israelis warned that militant Islamic groups were using London as a base the British authorities said they were 'crying wolf' again.
When Arab governments called for a clampdown on fundamentalists in London they were, according to one Arab diplomat, told they just wanted Britain to silence their Islamic opponents, and 'given a long lecture about freedom of expression'.
Now, the British security services have been compelled to turn to Middle Eastern intelligence agencies to find clues to the identity of those who last week bombed the Israeli embassy and a Jewish organisation in Finchley, north London.
Security services believe the bombs must have been planted by a 'sleeper cell' whose members had carried out extensive surveillance.
'They have been in London for some time,' said one intelligence officer. 'They knew exactly how the police would react to a suspect vehicle left unattended (outside the embassy).'
In private, Jewish leaders are angry with the Government. In the past few months, officers of the Board of Deputies of British Jews gave the police evidence that attacks on Jewish and Israeli targets were likely in Northern Europe.
It took no great intelligence coup to work this out, they said. The Lebanese press and Middle Eastern radio stations said that violence was likely. One Jewish leader said: 'The politest way to put it is that something has gone very badly wrong.'
Jewish organisations are also angry that, in private meetings, they failed to persuade John Major and Michael Howard, the Home Secretary, that membership of Hamas and Hizbollah should be illegal under the Prevention of Terrorism Act. Ministers also rejected calls to make it easier to prosecute the publishers of anti-Semitic and other racist literature.
Fundamentalist Islamic groups, particularly in the universities, have produced a stream of literature and posters which call for the killing of Jews.