A dramatic last-minute offer to buy Manston airport has been rejected this afternoon - just moments before staff began leaving for the last time.

US investors RiverOak made a third bid - believed to be around £7million - for the Thanet site three-and-a-half hours before 144 workers prepared to leave for the last time at 5pm.

But the 11th hour offer was rejected by owner Ann Gloag at 4.55pm - despite it matching her asking price and significantly higher than the investment firm's original £5million bid.

A spokesman for Connecticut-based RiverOak said Gloag gave no reason for the refusal in an email, other than to say it had come too late.

MP Sir Roger Gale - who has campaigned for the airport to stay open - arrived at the airport shortly before 5pm to meet chief executive Charles Buchanan.

Declaring that it "may not be the end of the line" for Manston, he revealed he is urging Gloag to grant another week for negotiations.

Around 200 members of the public gathered outside to say a tearful goodbye to the airport with a century of aviation history.

Crowds waving flags and banners booed as Mr Gale revealed to them the offer had been rejected as scores of staff prepared to leave after months of uncertainty for their jobs.

Mr Gale said: "There is absolutely no reason whatsoever why this airport should be closed tonight.

"The fact that people have been given notice is not irrevocable - that can be withdrawn.

"Mrs Gloag has said she is rejecting the airport on the same grounds she rejected yesterday.

"Laura Sandys and I have written to Mrs Gloag asking her for a further week. I have yet to receive a reply.

"If that week cannot be granted, I want to know why it can't be granted as there is no reason."

He handed over a flag to campaigners bearing the words "Save Manston" - and told protestors the fight continues.

"There is a lot more water to flow under this bridge," he said. "I am hopeful even now that Mrs Gloag realises she can do the deal that needs to be done.

"This is a very sad moment, but it may not be the end of the line."

The original £5m bid by RiverOak was made during the May Bank Holiday weekend and rejected the following day.

A day later, owner Gloag announced the site's closure, saying a consultation had failed to find a viable alternative.

A second improved offer was made earlier this week, but was rejected on the grounds of being too late.

Unite regional officer Ian McCoulough said: "Three months ago we had upset and unhappiness. What we have now is anger.

"Thanet is not a high employment area so Manston's existence is a great thing for Kent."

The last-minute drama unfolded as the airport prepared to close its doors for the final time, marking the end of a century of aviation history.

Protestors from the Save Manston and Why Not Manston? campaign groups gathered at the site, near Ramsgate, this afternoon to honour workers as they waved goodbye to the airfield founded during the First World War.

The final bid to save the airport came just hours after EastEnders star Cliff Parisi was involved in an emergency landing at the airport this afternoon.

The site was said to have been losing £10,000 a day and rumoured negotiations with low-cost airline Ryanair broke down last year after the company issued a profit warning.