'Nervous Shock' or 'Psychiatric Injury' must be a recognised psychiatric illness. Fear, distress or bereavement is not enough (Hinz v Berry), but pathological grief is (Tredget v Bexley HA). The courts recognise deseases specified in journals such as the WHO 1992 classification of mental and behavioural disorders.
Recognised illnesses include PTSD (Re GB, RB and RP - from sexual abuse) and clinical depression (Chadwick v BR). Grief can lead to PTSD (Vernon v Bosley)
NS may result in physical injury such as miscarriage (Bourhill v Young), heart attack and ME (Page v Smith).
McLoughlin v O'Brian  - created NS as separate category of negligence. Laid down the following 4 criteria which must be satisfied for a claim to succeed.
Alock v CC of South Yorkshire  and White v CC of South Yorkshire  are now the leading cases in this area.
Page v Smith  divided victims into primary and secondary victims. Primary victims are physically hurt or reasonably believed they were in danger (Dulieu v White). Normal rules of negligence apply, and claimants can recover damages for NS provided they can prove causation etc. The claimant does not need to show that he possesses "normal fortitude".
Atta v British Gas - NS could result from the destruction of property (e.g. Life works). Atta is unlikely to succeed today. NS is an inappropriate and inaccurate term, better to use 'Psychiatric Injury'.
Secondary victims are not primary victims, but may be in fear for others. It is more difficult for secondary victims to recover.
If a claimant can show that a person of customary phlegm would suffer illness, they can claim. The "Thin Skull Rule" (take your victim as you find them) means that once first hurdle is cleared, the claimant can claim for the full extent of any psychiatric injury. The "Thin Skull Rule" is generally called the "Egg-Shell Personality Rule" in NS.
Relationship between claimant and victim
Secondary victims may be able to claim if they have "close ties of love and affection" to those in danger. (Lord Oliver in Alcock). For example, parent/child or husband/wife. Hambrook v Stokes - a mother recovered damages for NS after witnessing a runway lorry heading towards her children. Individual case must be assessed on the facts.
In there is no relationship between a secondary victim and those injured, it is generally not possible to claim for NS. It is assumed that a reasonable man should have sufficient phlegm to withstand witnessing injury to others. Alock suggest that it may be possible in exceptional cases, but this was denied in MacFarlane v EE Caledonia. To recover (MacFarlane v EE Caledonia), a bystander must satisfy one of the following.
Proximity in time and space
Generally the claimant must be present at the scene, or it's immediate aftermath (McLoughlin). Hevican v Ruane  - a father recovered for NS after identifying his son in a mortuary. Disapproved. BUT W v Essex County Council the HL refused to strike out a claim for NS arising from the placement of a foster child with a family who sexually assaulted the daughters. It took some weeks for the parents to become aware of what was happening.
Manner of perception
The usual requirement is that NS is a "reaction to the immediate and horrifying impact" (Alcock) Sion v Hampstead HA (1994) - father watched son die slowly. Action failed. BUT North Glamorgan NHS Trust v Walters  - the claimant suffered NS after witnessing the death of her 10 month old baby over 36 hours after negligent medical treatment. Action succeeded.
The claimant must show that his perception was through his unaided sense, not second hand (E.g. by TV). The broadcast of events so horrifying so as to cause NS is generally a "novus actus". Broadcast guideline should shield the viewer from such events. Alcock considered the possibility that claims could arise in exceptional cases from live broadcasts (e.g. exploding hot air balloon full of children).
Originally claim by rescuers were allowed as a matter of policy (Chadwick v BRB, Piggott v London Underground).
No special treatment is ow given to rescuers. Chadwick v BR - the rescuer (train driver) was also deemed to be a primary victim. See also White v CC of South Yorkshire for discussion.
Alcock v CC of South Yorkshire - Leading case re NS. Case concerned claims arising from the Hillsborough disaster.
Brice v Brown  - No real injury, but mother was suffering psychiatric illness so was already susceptable. cf Page v Smith
Bourhill v Young - The collision of a motorcyclist and a car caused the claimant, a pregnant women, NS and resulted (possibly) in the still birth of her child. HELD: The motorcyclist did not owe the claimant any duty of care (no proximity).
Dulieu v White - A pregnant barmaid suffered NS and premature birth of her child after a runaway horse and cart crashed through the front of the pub where she was working. The barmaid was in fear for her personal safety, and her claim succeeded.
MacFarlane v EE Caledonia - A claim for NS brought by a crew member on board one of the Piper-Alpha rescue ships. He was the only crew member to bring the claim, and at no time was he in any danger.
Page v Smith  - A motor accident aggrivated a pre-existing condition (ME).