Senior ministers were "misinformed" about the risks of a nuclear meltdown at the Fukushima nuclear plant by the Government's chief scientific advisor, The Independent has learnt.
At a Cabinet meeting on Tuesday ministers were briefed on the "worst-case scenario" by Sir John Beddington. But less than 24 hours later the situation had deteriorated beyond even the most pessimistic private forecasts by Sir John. As a consequence, there was a significant delay in advising British residents to leave Tokyo and the surrounding area.
Yesterday a plane flew to Japan to be on standby to evacuate the British rescue teams working in the disaster zone in case of further leaks. The Foreign Office advised British nationals in Tokyo and to the north of the capital to consider leaving the area.
The Independent understands that both moves were ordered by ministers after they realised that earlier briefings had significantly underestimated the risk of a full nuclear meltdown.
"This has really spooked us," one minister said. "On Tuesday we were given a briefing by Sir John outlining the risk of nuclear leaks at the plant. He outlined a range of possibilities. But within 24 hours we were already in a position where things had already deteriorated beyond what he had described as the worst-case scenario. We were misinformed of the dangers."
Yesterday Sir John took to the airwaves to admit that the Government was now "extremely worried" about the situation and, in particular, the effect of fuel tanks leaking in plants five and six.
Sir John said: "We are worried about that. The reason we're worried is there is a substantial volume of material there and that this, once open to the air and starting to heat up, can start to emit significant amounts of radiation.
"If it starts to emit significant amounts of radiation then that will undermine the ability of the Japanese authorities to actually work in the vicinity because there will be a danger to human health. So that's why the situation has changed and why we're very worried."
It contrasts sharply with his position on Tuesday when, as well as briefing Cabinet, he told Britain's ambassador to Japan there was "unequivocally" no problem with radiation in the Tokyo area.
He said then: "What would be a reasonable worst-case scenario? If the Japanese fail to keep the reactors cool and fail to keep the pressure in the containment vessels at an appropriate level, you can get this dramatic word 'meltdown'... it's not serious for elsewhere."