The UK has no public nuclear alert system. SMS may be the answer

It's since been revealed the employee

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who sent the message clicked the wrong option from a drop-down menu – "Missile alert" rather than "Test missile alert". In the 38 minutes it took for officials to issue a retraction, people in Hawaii panicked, fled, and contacted love ones while fearing the end was nigh.

While the human-error came from a poorly designed user interface and a lack of safeguards – the Hawaii Emergency Management Agency has already introduced changes – the technical broadcasting of the system worked correctly. The false alert was quickly sent to mobile phones across the state. Hawaii's governor David Ige tweeted to say people in the country must have "confidence in our emergency alert system".

http://www.wired.co.uk/article/ballistic-missile-hawaii-warning-threat-uk-wea-sms