The terrorist "mastermind of a major conspiracy" yesterday entered a guilty plea in Woolwich Crown Court to a charge of conspiracy to murder. Dhiran Barot admitted planning a radioactive "dirty bomb" explosion which it was claimed would have caused "injury, fear, terror and chaos", and/or "fear, panic and social disruption". Barot also planned a coordinated series of attacks in the UK and US, with the "Gas Limos Project", involving three limousines filled with explosives and gas cylinders placed in underground car parks, being allegedly the principal attack planned.

The "mastermind" is claimed to have planned the attacks between 2000 and 2004, but the prosecution accepted that there was no evidence that he had obtained money to finance the plot, or that he had acquired bomb-making material, radioactive substances, limos or gas cylinders. Nor does there appear to be any indication that he knew where to source radioactive materials, how to build a dirty bomb, or how to set off sufficient gas cylinders in an underground car park to make a skyscraper collapse. Or indeed what the limo parking deal might be in the bowels of the World Bank HQ or the New York Stock Exchange, which were among the cosmopolitan list of targets.

Barat, who according to the Daily Mail was run to earth in a Harlesden barber's shop after a "dramatic chase", did have several attack plans in notebooks, and plans for the US attacks were "found on computers" after his arrest. Expert evidence, reports The Times, indicated that the dirty bomb would not have caused death "but, if constructed to Barot’s plan, would have spread enough radioactive material to make 500 people sick."

It is entirely unclear how a number so precise might be derived from the rough notes of an apparent amateur with no actual terror gear, but wreaking radiological havoc is no doubt one of the many things that fall into the category of being Easy for terrorists to... Realistically, the experts available to the prosecution will have said that the damage caused by a dirty bomb will be mainly that which is inflicted by the conventional explosives, and that the distribution of the radioactive material will depend on the size and construction of the conventional bomb used for this purpose. And they may have said that under certain conditions, depending, numbers of people might experience minor contamination. Or not, depending. And they may also have said that the radioactive bit of the mess created probably wouldn't be particularly hard to clear up.

Might they have said that the major effect of dirty bombs is the global hysteria the discovery of the plans causes? We wish...

Details of Barot's case were revealed when reporting restrictions were lifted following his guilty plea. The prosecution stressed that in admitting his guilt Barot was making no admission regarding the involvement of seven co-defendants in the conspiracy. These deny all allegations, and will be tried next year.

Barot's arrest was one of a number which took place in the UK in August 2004 following the arrest the previous month of Muhammad Naeem Noor Khan in Pakistan. Khan's arrest prompted a heightened security alert in Washington and New York City, and produced some intriguing reverberations in the US, detailed by Juan Cole here and here. ®