The casket will be pulled above 40,000 feet

It will take him up to three hours to reach a height of more than 40,000 feet (12,192 metres).

Hannah Cameron told BBC News Online: "Before he opens his parachute he will be the first man to break the speed barrier without using an aeroplane.

"We are building the balloon now, using a model section, and the attempt will be sometime between May and September."

The balloon will carry Mr Fournier up in a telephone-box shaped casket which will protect him from the ultra-violet light.

Michel Fournier: "Loves experimenting"

Once he has admired the view, he plans to cross the sound barrier just 30 seconds after leaving his casket.

His pressurised suit can withstand temperatures of -100 C, but he will have to inhale pure oxygen for four hours before he actually jumps.

Mr Fournier said: "I love life and life pays me back well.

"I love discovering and experimenting.

"I believe in my lucky star and in the virtues of courage and self-implication."

The site of the launch is yet to be announced, but if all goes to plan, the casket will fall to earth on another parachute before making a landing of its own.