"Partial exemptions"
"These include: ...
...Functions that, by their nature, require statutory (or prerogative) authority. This does not exempt an activity simply because statute provides an organisation with the power to carry it out (as is the case, for example, with legislation relating to NHS bodies and local authorities)...
...In relation to medical emergencies, section 6(3) states that the exemption does not apply to the administration of medical treatment but it does apply to a decision over which patient should be tended to first. For example an ambulance crew is deployed to the scene of a motorway crash involving multiple victims. They arrive at the scene and administer first aid to a victim with minor injuries, leaving a victim, with more serious injuries, to suffer without tending to them. There is no 'relevant' duty of care arising from the decision as to the order in which the patients are to be treated.
The ambulance service does not owe a relevant duty of care until the ambulance crew tend to a patient and administer medical treatment. Therefore it does not matter, for the purposes of the Act, how slowly they drove to the scene. It is also irrelevant for these purposes that the crew chose to ignore the more seriously injured. It is only when they tend to the patient that the organisation takes on a duty of care for that particular patient..."
http://www.cps.gov.uk/legal/a_to_c/corporate_manslaughter/ 