In the intelligence business, hindsight can sometimes uncover embarrassing misjudgments - a video shot here or a bugged conversation there that could have filled a vital gap in knowledge, leading to the prevention of a terrorist attack.

After the July 7 London suicide bombings in 2005, MI5 realised that its surveillance operatives had, unwittingly, caught in their net two of the main plotters, as they were keeping watch on other terrorist suspects engaged in a more immediate threat.

Mohammad Sidique Khan and Shehzad Tanweer were considered to be non-terrorist players, not requiring intensive surveillance in their own right, and their real pedigree as would-be bombers was not discovered until after they had blown up 52 people more than a year later.

Has MI5 now been caught out by another piece of hindsight in the light of the claim by King Abdullah of Saudi Arabia that his country’s intelligence service had passed on to the Security Service information prior to the July 7 bombings which, if acted upon, could have stopped the terrorist atrocity?

King Abdullah’s claim is not new. The Saudis made the allegation after the suicide attack, indicating that crucial intelligence had been given to the British that apeared to have been ignored.

However, a close re-examination of the Saudi intelligence by MI5 counter-terrorist experts, and subsequently also by the parliamentary Security and Intelligence Committee, which was shown the material, found that the accusation was full of holes.

The Saudis had provided general intelligence about a plot to launch terrorist attacks in the United Kingdom, but, according to security sources, there was nothing specific, and no detail indicating that suicide bombings were being planned against public transport locations in London.

On its website, MI5 states: “No prior warning of the attacks was received from any source. The Saudis provided information about possible planning for an attack in the UK which was materially different from the attacks that took place in London on July 7.”

The Saudi intelligence was thoroughly checked out, and was studied along with other “tip-offs”, by the Joint Terrorism Analysis Centre (JTAC), which is based at MI5 headquarters at Thames House on Millbank. None of the experts considered the Saudi intelligence had sufficient merit or credibility to sound the alarm, let alone to persuade JTAC to recommend a raising of the terrorist alert.

Even with hindsight, MI5 is of the same view today, that the Saudi intelligence titbits were not of themselves specific enough to be taken seriously, although had there been better information from other sources, it is possible the material could have played a part in drawing up a more precise picture of what was being plotted.

The exact wording of the Saudi intelligence has, of course, not been divulged, but security sources insist that there was nothing in the material to point the finger at any particular individuals or any detailed plot indicating timing and location. The Security and Intelligence Committee, chaired by Paul Murphy, the former Northern Ireland Secretary, agreed.

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