A Frencharchitect says he has cracked a 4,500-year-old mystery surrounding Egypt's GreatPyramid, saying it was built from the inside out.

Previoustheories have suggested the tomb of Pharaoh Khufu was built using either a vastfrontal ramp or a ramp in a corkscrew shape around the exterior to haul up thestonework.

Butflouting previous wisdom, Jean-Pierre Houdin said advanced 3D technology hadshown the main ramp which was used to haul the massive stones to the apex wascontained 10-15 metres beneath the outer skin, tracing a pyramid within apyramid.

Afterunveiling his hypothesis in a lavish ceremony using 3D computer simulation,Houdin told Reuters: "This is better than the other theories, because itis the only theory that works."

To prove his case, Houdin teamed up with a Frenchcompany that builds 3D models for auto and airplane design, Dassault Systemes,which put 14 engineers for 2 years on the project.

Now, an international team is being assembled to probethe pyramid using radars and heat detecting cameras supplied by a Frenchdefence firm, as long as Egyptian authorities agree.

Bob Brier, a senior research fellow from Long Island University attending the unveiling,said: "This goes against both main existing theories. I've been teaching themmyself for 20 years but deep down I know they're wrong.

"Houdin's vision is credible, but right now thisis just a theory. Everybody thinks it has got to be taken seriously."

'Durable development'

Egypt's SupremeCouncil of Antiquities was not immediately available for comment. Dassault saidBrier and other Egyptologists attending the ceremony were supporters ofHoudin's theory but had no financial links to him or the firm.

Houdin began working full-time on the riddle eightyears ago after a flash of intuition passed to him by his father, an engineer,and five years before actually visiting the site.

He found that a frontal, mile-long ramp would haveused up as much stone as the pyramid, while being too steep near the top. Hebelieves an external ramp was used only to supply the base.

An external corkscrew ramp would have blocked thesight lines needed to build an accurate pyramid and been difficult to fix tothe surface, while leaving little room to work.

Houdin said: "What characterised the Egyptianswas their sense of perfection and economy.

"We talk of durable development now, but it wasthe Egyptians who invented it. They didn't waste a single stone. They reliedpurely on intelligence."

Houdin also claimed to have shed light on a secondenigma surrounding the purpose of a Grand Gallery inside the pyramid.

The Frenchman believes its tall, narrow shape suggestsit accommodated a giant counter-weight to help haul five 60-tonne granite beamsto their position above the King's Chamber.

He thinks that no more than 4,000 people could havebuilt the pyramid using these techniques rather than the 100,000 or so assignedby past historians to the task of burying the pharaoh.