Mobile firm Three has been fined £1.9 million for failing to ensure all its customers could always call 999.

Telecoms regulator Ofcom announced the fine today after it uncovered a weakness in part of Three's emergency call network which meant it could not guarantee emergency calls from some areas could always be made during an outbreak of technical setbacks.

Three admitted some customers would have been unable to make 999 calls during an "unforeseeable" outage on 6 October last year, and has taken steps to improve its network resilience.

What happened?

Three said it suffered an "unprecedented and unforeseeable" 'fibre break' outage which caused a loss of service in Kent, Hampshire and parts of London. It said it was quickly resolved, but has declined to say how long customers were affected for.

After Three reported the outage to Ofcom, the regulator investigated and found Three should have been able to automatically divert emergency calls via a back-up route. Three has now added an additional back-up route for emergency calls.

An Ofcom spokesperson said: "The breach of the rules was not the incident itself, but rather the weakness identified in Three's network.

"Ofcom has today imposed a penalty of £1,890,000. Our investigation found that Three did not act deliberately or recklessly. However, the fine reflects the seriousness of the breach, given the potential impact on public health and safety."

The fine includes a 30% reduction because Three co-operated with the investigation, and it will be passed to the Treasury.

A Three spokesperson said: "Providing our customers with uninterrupted access to emergency services is a requirement we take extremely seriously.

"Three therefore acknowledges Ofcom's decision today to fine for a single point of vulnerability on [our] network. However, this vulnerability has not had any impact on our customers and only relates to a potential point of failure."