A series of five-day long strikes by junior doctors could force the NHS to cancel up to half a million operations and four million appointments, a health boss has suggested.
Chris Hopson, chief executive of NHS Providers, which represents frontline NHS leaders, said the actions would cause "unprecedented" disruption to patients.
"We're talking about four sets of five days of strikes," he told BBC Breakfast.
"That's equivalent to half a million - 500,000 - cancelled operations and four million lost outpatient appointments, so what we're talking about is a completely unprecedented scale of disruption and negative impact on patients; it's extremely worrying."
The medical regulator has urged junior doctors to seriously consider whether or not to take part in a new wave of strikes.
A five-day strike by junior doctors has been called in the ongoing dispute over contracts, but what does it mean for patients?