The £20m contract was signed and sealed yesterday, and greeted with joy by the 110 staff at Rolls-Royce Marine Electrical Systems, in Northarbour, Portsmouth.

The contract means their jobs are safe for two years, and that another 15 staff will now be recruited.

They will build the electric cables and systems for the two huge 65,000-tonne Royal Navy ships called HMS Queen Elizabeth and HMS Prince Of Wales.

The £20m local contract with the Ministry of Defence is part of a larger £235m deal involving several firms, which will build the gas turbines, generators, motors, propellers, steering gear and rudders needed to power and steer the vessels which are due to go into service in 2014 and 2016.

Such are the size of the £4bn ships that four diesel engines and two gas turbines are needed to create 109 megawatts of electricity to power each ship – enough to supply a town the size of Swindon.

And it will be the skilled Rolls-Royce workforce at Northarbour who will be responsible for making sure that all the latest electrical cabling between the engines and other parts of the ships will all work.

The director of Rolls Royce Naval Marine, Ken Stevenson, said: 'This is excellent news for our people in Northarbour. It's the biggest contract we've ever worked.

'It continues the support of the Royal Navy that we've done for many years.'

Rear Admiral Bob Love said: 'It's about sustaining existing jobs in Portsmouth. The carriers are going to be based here.

'They'll require fuel support, food and the logistical requirements a big ship will need. They'll be a big presence in the town.'

And even though the new carriers will be three times the size of the current carriers – HMS Illustrious and HMS Ark Royal – they won't need a larger crew as more of the ships' functions will be run automatically by machines.

Rear-Adml Love said: 'Machines are much more reliable than they were. If you think of a car these days you expect it to start. That wasn't the case 30 years ago. And with greater reliability we have six engines. If one needs maintenance then we can cope with that.'