Hospital security staff have gone on strike in a dispute over safety and pay.
Mitie Security workers, represented by Unite, began the action at Southampton General Hospital at 07:00 BST.
Unite said the company's 21 staff at the hospital were regularly attacked by people under the influence of drink, drugs and with mental health problems.
Mitie said patient safety was "paramount" and had arranged cover until the walk-out ends at 14:00.
The union said staff were not given enough personal protective equipment such as stab vests and safety restraints.
Unite spokesman Scott Kemp said security officers wanted to be paid £10.50 per hour and their supervisors £12.16 per hour for doing the "dangerous job".
He added: "Unite's door remains open for constructive talks 24/7 over this Easter holiday period."
Mitie said its offer to increase security officer pay to £9.50 per hour equated to a 14.5% rise in the past seven months. It added that the supervisors are paid £10.30 per hour and are based in control rooms.
In a statement, the company said: "The number of incidents has remained static over the past three years, as has the number of staff injuries.
"None of our staff have been directly targeted and the number of incidents occurring at Southampton is relatively low."