The £1.51 billion sale of Gatwick airport has formally been completed with unions anxious that the new owners preserve jobs and protect working conditions.

Airport operator BAA has sold the West Sussex airport to US-based investment fund Global Infrastructure Partners (GIP) which already owns London City Airport.

First announced in October, the sale was given European regulatory clearance last week and has now been finalised.

Steve Turner, national officer for the Unite union, said the sale ended "months of frustration for our members over the future of Gatwick operations and their very employment".

He went on: "We now look forward to further developing our relationship with the GIP team, which brings considerable operating experience to the airport.

"Reinforcing existing commitments on future stability and security of employment for our members, alongside a clear long-term investment strategy, are now our core objectives for the coming weeks."

BAA had already decided to off-load Gatwick even before the Competition Commission ruled it must sell the airport as well as Stansted and either Glasgow or Edinburgh airports.

The commission's ruling came after it found that BAA's ownership of seven UK airports was anti-competitive.

The new Gatwick airport board is being chaired by Sir David Rowlands, a former Permanent Secretary at the Department for Transport, who is heading the Government-appointed High Speed 2 company which will shortly report on the feasibility of a north-south high-speed rail line.

Sir David has already promised more-efficient operations at Gatwick and a "relentless focus on customer service".