NEW: UK authorities were closely monitoring increased threats to RAF Fairford and had tightened security at the airbase before the attempted attack was foiled, according to people familiar with the matter.

Investigators are considering the base being targeted in response to the Iran war as the most likely motive in the early stages of their investigation, although they caution that other motives have not been ruled out. It is being considered a serious attempted attack.

Trump said Sunday that “we had them under view for a long time”, however a local farmer told British media that she had seen a group of men wearing balaclavas near the base just after midnight on Sunday and called the police, raising questions about whether the plot was on the radar of the security services.

The reality may be somewhere in between, and both things could be true at once.

While UK authorities were closely watching for increased threats to the base, they are grateful to the member of the public who called the police, the people familiar with the matter said. That suggested that, while there was knowledge of the increased threats, it may have been the local resident who alerted them to the apparently imminent attack.