Croydon hospital declares 'internal major incident'
Croydon University Hospital in south London urged people only to go to attend A&E in a genuine emergency because of high demand.
The hospital declared an "internal major incident" lasting several hours.
A spokesman for Croydon Health Services NHS Trust said the heightened state of focus on front-line service was stepped down after a few hours.
The trust said it was "stretched", but blue-light ambulances were not turned away at any point.
A number of hospitals in the UK have recently declared "major incidents".
If a hospital declares a major incident or internal incident, it is a sign that things have got exceptionally busy and special measures are need to cope.
The declaration allows hospital bosses to call in extra staff to help.
Croydon University Hospital declared an "internal major incident" at 07:00 GMT and by 14:00 it had been downgraded.
A spokesman said: "Like a number of NHS hospitals, we are currently seeing a very high number of people in our A&E department, many of who require admission into hospital.
"To increase our capacity we have put in place a series of actions to help meet this increased demand."
NHS England said an internal major incident is activated when a trust is under significant pressure that is internal to the organisation.