Not for the first time, the Observer provides the clearest, fairest and most authoritative account of the latest instalment of the defence against terror. The accounts in the rest of the media in the past few days about the American warnings and then the arrests in Britain of al Qaeda suspects have been quite bewildering. First, there were the warnings from US Homeland Security about imminent threats to various US landark institutions, round which rings of steel were hastily erected. Almost immediately, the appeaseniks started claiming that the whole thing was a post-Democratic Convention stunt by President Bush -- a riff that went into hyperdrive when some unnamed intelligence operative (again) sniffily dismissed the newly discovered terrorist plans as pre-9/11 antiques. But then the following day the British police executed one of the largest raids on al Qaeda suspects, netting one person in particular described as Osama bin Laden's numero uno in the UK.

So what was this: a Bush stunt; or a genuine anti-terror breakthrough; or a genuine breakthrough which was prematurely hyped by the Americans so that the Brits had to hastily activate a swoop before it was ready? The stunt claim is of course a ripe piece of Michael Mooreite grotesquerie, which says everything about the people making such a claim and nothing about anything or anyone else. The Observer, in a calm, well-informed piece of reporting, indicates that the arrest of Mohammed Khan in Karachi on July 13 was a major breakthrough of the first importance. It uncovered not only a key operative and a huge amount of astonishingly detailed information about US and British targets, but although this research had been conducted in 2000 or 2001, the Pakistanis said that the threat 'was present'. That's why the Americans went into crisis alert mode.

A classic sting was then set up to track down Khan's terrorist contacts before they could activate these plans. Khan was forced to email them, and many duly fell into intelligence and police traps. But according to sniffy British sources, the arrests were the result of a long-standing intelligence operation that began long before the American alerts. Clearly, someone somewhere blew the whistle too early about Khan's capture, precipitating a scramble to arrest suspects before they disappeared. As the Observer soberly concludes, however, whatever the blow dealt by this operation to al Qaeda's plans, it is by no mens the end of the organisation. Bin Laden remains elusive and above all alive. The hydra has many more heads, alas.

What is clear, though, is that it was a major break for the anti-terror agencies, and plans posing a clear and present danger were interrupted. But there is another fact which appears to have escaped attention. The appeaseniks sneer that the reconnaisance of targets was old, pre 9/11 activity. Very well. Yet now look at this:

'According to Pakistani officials, there was also evidence of preparations for an attack on Heathrow by British-based activists. There were photographs of terminal buildings and the refuelling centre, as well as of tunnels used by passengers and freight companies. Precise measurements of roads, buildings and underpasses had been recorded. Intelligence sources elsewhere in the region told The Observer last week that the reports had included surveys of underground parking lots so detailed that the gradient of the ramps had been noted. The same sources said the planning also recorded traffic flows on roads around the airport, as well as details of the sequences of traffic lights around the perimeter'.

It has been a constant appeasenik refrain that Britain would never have become an al Qaeda target had Tony Blair not gone poodling up to President Bush and allied Britain to the defence against terror. Yet it appears that this 'old', pre 9/11 reconnaisance activity included targets in Britain. If this is true, it is the first hard evidence that the targeting of Britain was nothing to do with the reaction to 9/11 -- because it was a target before that event took place.