Driving home from a party in the early hours of yesterday, a local farmer was shocked to see three large white vans blocking a road in her quiet village.

Suspicious that a mobile number on one of the vans was a digit short, she turned her car around, only to see men in balaclavas fleeing into the trees and across the fields.

Five men were later arrested but the woman claimed she had seen more suspects – as police carried out a helicopter 'search' operation overhead.

The men were heading towards nearby RAF Fairford – an airbase used by the United States Air Force for operations against Iran. The base, which is already on high alert and had ramped up security in recent weeks, is less than a mile from the centre of the village.

Minutes later armed police descended on the quiet Cotswolds village of Whelford – home to just 100 – and arrested five men. Dramatic video and pictures from the scene show the young, shirtless men sitting on the ground – arms handcuffed behind them.

The woman, who did not want to be named for fear of reprisals, said she believed her headlights had startled the men, prompting them to try to flee.

'They probably thought we were the police [and] panicked,' she said.

'A plucky amateur shouldn't be spotting an unusual bit of activity at 1am when the air base is on high alert. I think it's absolutely astonishing.

'Thinking about it now, and what could have happened if they had tried to stop me from driving away, I am quite lucky.'

She added: 'It is pretty incredible, realising you had a brush with potential terrorists face to face and may have foiled a terrorist plot. It was clear they had just got there. Thank God we spotted them.'

The woman said she believed she had spotted more than five men - despite just five being arrested.

She told the Sun: 'The worst thing is that we saw more than five people and they kept saying they arrested five. They had the helicopters searching.'

It comes as Temporary Chief Constable for Gloucestershire Police, Maggie Blyth, has indicated the force is not looking for anybody else in connection with the incident. 

The farmer revealed she had been driving along a quiet lane through the village while her husband was sleeping beside her as she prepared to drop a friend home.

She said the vans struck her as being suspicious because a phone number and lettering on the back of the vehicles appeared to be fake.

She added: 'I just thought what the hell are they doing… I saw a group of Middle Eastern–looking young guys running off through the trees. Some of them had masks or balaclavas on, and they all scattered ahead of us as we drove back past.

'Some of them ran into the fields, and some of them turned to run towards the air base. We realised this was something pretty serious.

'We knew the air base had a credible threat of a terrorist attack before last night. So as soon as I saw them I was worried.

'I mean, you don't see masked men running around at half–one in the morning in the countryside near a secure air base and not have concerns.

'It's bloody preposterous that they weren't on it and I had to phone up.

'I'd like to think it's a once-in-a-lifetime thing.'

The woman said she hoped the police 'sort themselves out and this doesn't happen to us again' – insisting there would be some 'red faces in the highest levels of command at Fairford anyway'. 

One of the white vans was labelled 'FUEL 2YOU' in red lettering, with a phone number that was one digit short.

A company with the same name said it had two vans and they were both in London yesterday. After the men were detained a 400m cordon was thrown up around the vehicles – which appeared to have been laden with barrels – while police went door to door, evacuating the 85 homes in the village.

Residents told how they were initially woken by a helicopter at 1am and then again by bangs on the door before being taken away in their pyjamas and dressing gowns to a leisure centre.

Jo, who did not want to give her surname, has lived in Whelford for 18 years. She said she was evacuated from her home at around 7am, adding: 'We were asleep and they were just banging on our door. They said it was a critical incident and we've got to leave straight away, and they basically wouldn't leave the doorstep until we left.

'We just had to throw our clothes on and come. We didn't know anything. (The police) literally waited (at the door). I didn't even brush my teeth.'

Another Whelford resident said they were woken by a helicopter at 2am. They were then woken again at 6.30am by police officers banging on their bedroom window telling them they needed to evacuate. The local said: 'We'd gone to bed as normal around 10pm and heard the helicopter above the house at 2ish.

'You get used to aircraft living so close to the base, but not at that time in the early hours. So we knew something was happening.

'We sleep downstairs and heard a banging on the window at 6.30am. We must have slept through the doorbell.

'It was the police, they were armed and in masks. They very calmly said there was a 'serious incident' and that we needed to leave for our own safety.

'We grabbed some things and headed to the leisure centre. We haven't been told when we can go back. It's been a very scary day.'

Those evacuated were taken to Cirencester Leisure Centre – ten miles away – where areas are also being set up for people's cats and dogs.

Two uniformed officers had earlier gone to collect one worried resident's dog. They dropped off the small black terrier to her in the foyer of the centre.

The local farmer was hailed a hero last night.

She had reportedly first tried to alert police at the base but no one answered the phone – prompting her to dial 999.

One resident said: 'She is a hero.

'She has almost certainly prevented a terror attack.'

Julian Tudsbery, who has lived in Whelford for 30 years, said: 'Evidently, they phoned the airbase police, who didn't answer the phone. It just rang out so she dialled 999.'

He said he was evacuated at 7am, adding: '[The police] were then banging on the door, so I went downstairs in my dressing gown.'