Doctors have joined picket lines at NHS hospitals across the country as they begin the first all-out strike in the organisation's history.
There were several dozen medics in place at King's College Hospital in Denmark Hill, south London, for the walk-out's scheduled 8am start.
They put up banners with slogans including "Junior doctors striking to save your NHS" and "5 into 7 doesn't go".
There were supportive beeps and shouts from several passing cars and cyclists, and one motorist who shouted "get back to work" as he went by.
Accident and emergency Dr Tom Roberts, 28, said he was striking because of the "unfair and unsafe" contract proposed by Health Secretary Jeremy Hunt that would leave many doctors "underpaid and over-stressed".
Dr Roberts, originally from Perthshire, told the Press Association: "We believe this contract will spread doctors too thinly across the ground and the NHS, from August if he goes through with this, will be unsafe for everybody.
"The BMA and junior doctors ... have asked Jeremy Hunt on so many occasions to just come and talk again, and he just tweeted responses to well-meaning questions.
"It is very, very frustrating for us. He just doesn't want to face doctors, he doesn't want to talk to us."
John Moore, a junior doctor in Newcastle, said: "I think Mr Hunt has mishandled this dispute from day one. He has refused to listen to any advice, even from his own MPs and researchers.
"He's misused statistics, he's outright lied, he's worried the public into not attending the NHS when they need to, and I think he should resign.
"He's completely lost the trust of an entire profession so unfortunately I don't see a route back to negotiations with him.
"But we are always happy to negotiate as we don't want to go on strike, so when there is a new health secretary I'm sure we will have more fruitful negotiations with them and I'm confident a deal can be reached.
"Let's not forget the BMA reached an agreement with the NHS employers but Jeremy Hunt personally vetoed that deal - he is the problem."