Brendon Sewill, chairman of the Gatwick Area Conservation Campaign, said: 'We have always been totally opposed to a new runway on environmental grounds, and have had massive support from across Surrey, Sussex and west Kent.
"We have been supported by all the local MPs and all the county, district and parish councils in a wide area. If necessary, we will resume the battle."
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The 24-year-old was unarmed and the incident is not being treated as terror-related.
Some platforms have been taken out of service with disruption expected to continue until the end of the day.
The Met Office has extended its weather warnings for snow and ice to cover vast swathes of the country, including London and the South East.