Westminster Bridge was shut to traffic on Sunday afternoon as hundreds of people joined a sit-down protest against the Government's health bill organised by the UK Uncut direct action group.
The protestors, many wearing surgeons' scrubs, began to sit down on the bridge as Big Ben struck 1pm.
Those taking part included comedians Josie Long and Mark Thomas, as well as Green Party mayoral candidate Jenny Jones AM.
A giant 'Save our NHS' banner was unfurled between two tripods set up in the middle of the bridge.
Westminster Bridge was chosen for the stunt because it links the Houses of Parliament with St Thomas' Hospital.
Although most of the crowd had gathered on the western half of the bridge, St Thomas' Hospital had taken extra security measures with metal barriers erected at the hospital entrance to keep protestors at bay.