The government is set to approve a £1bn purchase of military helicopters from the UK's only specialist factory. Italian company Leonardo's plant in Yeovil, Somerset, had been left in limbo after a planned visit by Defence Secretary John Healey to award the contract was cancelled on Thursday. But Treasury sources have told the BBC the deal to build a fleet of 23 defence helicopters will be signed off on Friday, after all. Leonardo's chief executive, Roberto Cingolani, has previously said the factory's future would be at risk if it was not awarded the contract. Britain's last military helicopter manufacturing site employs 3,000 workers and was the only remaining bidder for the contract. It is understood that the chancellor and prime minister chose to intervene to ensure the project would go ahead, in part to protect UK jobs. The Chancellor, Rachel Reeves, did not want the deal to collapse on her watch, because security and growth "were fundamentally connected", a Treasury source said.…