Major hospitals in London have declared a critical incident after a cyber attack led to operations being cancelled and emergency patients being diverted elsewhere.

It applies to hospitals partnered with Synnovis - a provider of pathology services. King’s College Hospital, Guy’s and St Thomas’ - including the Royal Brompton and the Evelina London Children’s Hospital - and primary care services are among those affected.

The incident has had a “major impact” on the delivery of services, especially blood transfusions and test results.

A spokesman for King’s College Hospital confirmed it had been affected by the attack.

The incident is thought to have occurred on Monday, meaning some departments could not connect to a main server.