The aircraft arrived from RAF Coningsby in Lincolnshire, swooping in low over Ruislip Gardens at about 11.40am.

The fourth to arrive performed a 'touch and go' manoeuvre, briefly touching down before taking off again to circle the base then land. Its take-off was the loudest part of the operation, and would have been audible in nearby communities.

They are there as part of Exercise Olympic Guardian, a practice run for the games this summer, when the aircraft will be stationed at RAF Northolt for the duration of the Olympics and Paralympics, helping to provide air security for the London and south-east England area.

For the next week they will carry out a series of flying exercises, including a night flight intended to end no later than 10.30pm. Bank Holiday Monday has been designated a 'no fly' day, and they will depart on May 10.

Joining them at the airbase in West End Road, Ruislip, are Sea King helicopters being used for airborne surveillance.

The Typhoons will return shortly before the Olympics begin in July, when they will be fully armed.

RAF Northolt commanding officer, Group Captain Tim O'Brien, pictured, was at pains to reassure the base's neighbouring communities that safety and noise control were top priorities, and he said how grateful he was for the support and understanding of the situation he had received from residents' groups and Hillingdon Council, and the sense of pride he had discovered among local people that RAF Northolt should be chosen for the security role.

He promised aircraft noise would be kept to a minimum and weapons safety was paramount. "Armament safety is something we are really good at," he told the Gazette.

"The Typhoon is unusual," he said. "It's not especially noisy but it's a different type of noise.

"On departure there's a bit more noise, but we have put a lot of measures in place to mitigate that."

And he said during both the exercise and the games, his staff would be monitoring noise levels.

During the games themselves, aircraft movements in this area will be prohibited without permission. Even Heathrow Airport must comply with certain restrictions.

Local pilots using Denham Aerodrome will have to file a flight plan, for example, and Typhoons may have to scramble to intercept and check any unidentified aircraft entering the vast control zone.

For those living close to the base, daily life during the games will not change much. In fact there will be fewer air movements because the commercial side of RAF Northolt will be curtailed.

If a Typhoon has to take off it will be of necessity, either on a sortie or for technical reasons, such as an engineering requirement.

The base has made a few modifications - many of them impossible to see from outside - such as temporary hangars for the fighters, temporary accommodation for pilots and ground crews and some changes to the apron and perimeter fence.

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