"We can't delay the take-off, because it's possible there will only be the one launch slot this year," he said, looking at the military airbase where the balloon and three-man capsule were having their final tests yesterday. "Rory [McCarthy] is not very well, but otherwise everything couldn't be looking better."
Mr McCarthy, 36, a businessman and amateur daredevil, was hoping to fly with Mr Branson, along with the professional balloonist Per Linstrand, 47. But he has a bronchial infection which doctors feared might develop into pneumonia. He was due to be woken at 4am this morning to see if he was fit enough for the flight - which, if it succeeds, will break the last great aviation record. At the airbase yesterday he posed happily for photographers.
"It is not down to the doctors, it is up to Rory" said Mr Branson last night. Earlier he had said Mr McCarthy was determined to go: "If he feels he's up to it, he will. But there's a risk to him because we'll be so high, and the air so depressurised, that it could damage his lungs."
Meanwhile, the countdown began last night on the desolate base, just outside Marrakesh, in southern Morocco, towards a take-off in the hours just after dawn today. Ground staff were poised to make the first of a series of irrevocable moves towards lift-off, by beginning the inflation of the two-tonne canopy of the balloon with pounds 100,000 worth of helium. That will take 12 hours, and once inflation has begun it cannot be stopped.
There is only enough helium for one attempt. Getting enough for another inflation would take at least a week. But a spokesman for Virgin, one of the principal sponsors, emphasised that the launch could be aborted at five minutes' notice if the weather conditions were unsuitable, although Mr Branson's readiness to leave behind his team-mate indicates the determination he has to complete the trip this time.
There are two reasons for that determination: first, two rival ballooning teams - one in the US and another in Switzerland - are preparing for an assault on the record. Second, the weather conditions are ideal, with a continuous jetstream - air travelling from west to east at about 30,000ft at speeds of up to 200 mph - girdling the globe around the Tropic of Cancer.
Almost exactly a year ago, Mr Branson waited here nearly a fortnight for the right conditions. But bad weather and unseasonal wind patterns, with a discontinuous jetstream, made a launch unfeasible.
The journey will take at least 18 days, crossing India and Japan at a height of 30,000ft - as high as commercial airliners - and aiming to finish in Britain. The crew will live in a capsule with just 100 sq ft of space, heated and powered by propane tanks attached to the outside, which will also heat a balloon inside the helium canopy to control their height.
Despite seeming a little less boisterous about the project than a year ago, he said: "I really enjoy the fact that the day has finally come. We're going to have a great adventure."
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