A worldwide Microsoft outage has disrupted emergency services, schools and parts of government in London, with normal service still not restored more than 12 hours after problems began.

Dozens of institutions across the capital have been affected, alongside millions of users worldwide. Teams, Outlook and Copilot are among the services experiencing disruption, which was first reported at around 6pm on Thursday.

A Downdetector heatmap showed London had the highest number of reported outages by region since the problems emerged. That measures user reports, rather than establishing the extent of disruption within individual organisations.

Microsoft said its efforts to fix the problem were not “taking as expected”. The company subsequently reported “early signs of stabilisation”, although services had yet to return to normal. The problem is understood to involve overloaded servers; Microsoft said it was not caused by a cyber-security attack.

The prolonged interruption has drawn criticism from Professor Awais Rashid, professor of cyber security at the University of Bristol. He described the failure to find a fix as concerning, given organisations’ growing dependence on third-party services such as Office 365 for their daily work.

“Whether a cyber security incident or not, their resilience is important to ensure businesses large and small can continue their daily operations,” he said.

Rashid also questioned whether Microsoft fully understood the underlying cause. His criticism concerns both the initial overload and the company’s ability to resolve it.

For organisations reliant on the affected services, the distinction between an attack and a technical failure does not remove the operational problem. Microsoft’s reported stabilisation offers some indication of progress, but it does not yet amount to restored service.