In 1957, a huge fire started at Windscale Piles chimney at Sellafield, spreading radioactivity across the Cumbrian countryside.

Due to the high levels of contamination, workers have only recently been allowed to enter parts of the chimney.

The demolition will cost British Nuclear Fuels (BNFL) an estimated �100m and take another four years to complete.

Radioactivity levels

Contractors are currently taking the chimney apart bit-by-bit and reducing radiation.

Just two months ago, only remote control machinery was allowed into the chimney where the contractors are working.

Even now, they can only stay in the chimney for about 50 minutes a day as the radioactivity levels are so high.

Jim Whitehead: 'Hazards'

Jim Whitehead, project manager at BNFL, told BBC Look North it was a hazardous operation.

"We have radiological-type hazards and, on a project like this, there are numerous conventional safety hazards because of its height.

"It is one of the tallest structures on the site itself.

"We have specialist contractors who are used to working at height and there are steeplejack experts."

"These are the first people to go in since 1949 when the chimney was built."

Good condition

Mr Whitehead said the fire - which at the time was the world's worst nuclear accident -had contaminated the chimney.

"There wasn't actual damage, if you think of damaged and twisted metal, there was nothing like that

"It was mainly contamination, that you cannot see, that was the effect of the fire.

"The steelwork and concrete is in remarkably good condition for its age.

"Radiation levels are very low now."