A £269 million helicopter-borne surveillance system has been ordered by the Government to protect the Royal Navy's new aircraft carriers.

Minister for Defence Procurement Harriett Baldwin visited Portsmouth Naval Base to announce the contract with Lockheed Martin, which will secure more than 200 jobs.

The Crowsnest system, which will provide long-range air, maritime and land detection and tracking, will be fitted to Merlin Mk2 helicopters that will be tasked with protecting the Queen Elizabeth class aircraft carriers and other Navy warships.

Ms Baldwin, who visited the Type 45 destroyer HMS Dragon, said: "Crowsnest will provide a vital intelligence, surveillance and tracking system for our new Queen Elizabeth class aircraft carriers, capable of detecting any potential threats at sea.

"Backed by our rising defence budget, and our £178 billion equipment plan, Crowsnest will help keep our armed forces safe as they deploy in every ocean around the world for decades to come."

The deal will sustain 90 jobs at Thales in Crawley, 60 jobs at Lockheed Martin in Havant, Hampshire, and 60 jobs at Leonardo Helicopters in Yeovil, Somerset.

The design is made up of a single mechanically scanned radar head, which uses an innovative system to provide 360-degree visibility from the underside of the helicopter, which then folds up to the side of the aircraft when not in operation.

Tony Douglas, chief executive officer of the Ministry of Defence's Equipment and Support body, said: "Crowsnest will play a key role in protecting the Royal Navy's future fleet, acting as the eyes and ears for the new Queen Elizabeth class aircraft carriers.

"This state-of-the-art project will demonstrate how we are providing world-leading, innovative equipment to our armed forces."

Ms Baldwin was also informed of final preparations being made for the two 65,000-tonne carriers, the first of which - HMS Queen Elizabeth - is due to arrive later this year.

Improvements to the Hampshire dockyard include reinforcing 905ft (276m) of jetty with more than 3,300 tonnes of new steel work, installation of new navigation lights in the harbour and Solent, and delivery of huge new fenders and gangways to accommodate the giant ships.

Other work includes dredging of the harbour to accommodate the carriers' vast size, including the removal of more than three million cubic metres of clay, sand and gravel with debris already cleared, including unexploded ordnance, cannons, and large anchors - some around 100 years old.