NHS England says services are back online after the global IT outage, but there could still be disruption.

The incident has sparked concern over the vulnerability of the world's interconnected technologies.

A mass IT outage has caused chaos around the world, with major airlines among the victims.

Ultimately, when systems wobble, there is little that can be done - except wait for a fix.

Experts say the manual fix required means it could take days for big organisations to get back to normal.

Cyber-security firm Crowdstrike said its update had caused the problem on computers running Windows.