RAF Fylingdales will soon be upgraded with new technology

American contractors are in charge of the work at the base on the North York Moors, but they have employed local builders and electricians.

It will be another year before the new defence system is tested and fully operational.

The Ministry of Defence says there will be no change to the outside of the base and no increase in radiation emissions.

Faster computers

Work to upgrade the early warning station at RAF Fylingdales will be carried out by Boeing.

Boeing's work includes installing faster computers, new communication links and modern graphic displays.

Boeing has also been awarded a contract for 15 ground-based interceptor missiles as part of the defence system which is due to become operational later this year.

Altogether the work is worth $823m (�449m) to Boeing.

The work to upgrade RAF Fylingdales was allowed to go ahead quickly as officials at the North York Moors National Park Authority decided it did not need planning permission.