The new contract for junior doctors in England will begin to be rolled out from today.
Junior doctors have staged several strikes in protest at the imposition of the contract, which the Government says will help reduce death rates in NHS hospitals at weekends but the British Medical Association (BMA) fears will have a negative effect on staff and patients.
From today, some obstetrics and gynaecology trainees will transition to the new terms and conditions of service.
The BMA described it as a "watershed moment for the NHS" and has written to NHS trust chief executives asking them to pause the introduction of the contract if certain conditions are not in place.
Last week, campaign group Justice for Health lost a High Court challenge against Health Secretary Jeremy Hunt over the new deal.