Barts Health NHS Trust -- which incorporates five hospitals across East London, and has a workforce of over 15,000 staff to provide care to millions of people each year -- has warned patients that some appointments and operations scheduled for Tuesday 23 May have been cancelled in the interests of safety following widespread IT disruption.
"We activated our tried and tested contingency plans, and are steadily bringing our clinical systems back online," the trust said.
"We are only now beginning to regain access to emails, for example, although there is a huge backlog of messages to be processed so it may take time before we can answer any queries that have been sent in by members of the public," it added.
"All of our hospitals remain open for emergency care, and we are accepting ambulances. However we have cancelled a small number of planned operations and clinics on Tuesday to ensure we can continue to run all services safely," Barts Health said in a statement.
The vast majority of planned surgery and outpatient appointments will continue at each of Barts' hospitals -- Mile End Hospital, Newham University Hospital, The Royal London Hospital, St Bartholowmew's Hospital, and Whipps Cross University Hospital -- including all all renal dialysis services.
Barts is attempting to directly contact all patients who are set to have appointments cancelled, but there's the prospect that some will only learn about the cancellation when they arrive.
"It is possible that we will not be able to contact all patients that we need to speak to, so we apologise if we are unable to proceed with your treatment once you arrive at hospital," said Barts.
The Trust also notes that all the hospitals remain open for emergency care and are accepting ambulances and that "clinically urgent appointments" will be prioritised wherever possible.
"Thank you for your continued patience and cooperation as we work to resolve these issues," the hospital statement.
In addition to continued disruptions at the hospital, some GP services in North East London are still experiencing issues, with clinics urged to submit suspected cancer referrals by fax. However, the services themselves are running and "care remains safe and consistent". The Trust is looking to return services to normal soon.
"Thank you all for your continuing support. We are working hard to get our services back up to normal," it added.
While Barts is still experiencing disruption, the vast majority of those hospitals affected have since managed to return services to normal following the WannaCry outbreak and cancelled patient appointments are being rescheduled.
At the time of writing, only around 300 payments have been made to the Bitcoin wallets tied to WannaCry, with those behind it so far netting just $108,000, a small amount when compared with the most successful ransomware campaigns.