Since it was foreseeable that Martin would suffer physical injury, Emma would be liable for his psychiatric injury. This principle is derived from Page v Smith [1995] AC 155, where Lord Browne-Wilkinson stated that even though the defendant could not foresee the exact type of psychiatric damage suffered by the plaintiff, the defendant still owed a duty of care to prevent foreseeable damage, including psychiatric damage. This is often referred to as the "eggshell skull" rule, which implies that a defendant must take the claimant as they find them, including any pre-existing conditions that may exacerbate the harm caused by the defendant's actions. 

Key Point: The Page v Smith case illustrates that foreseeability of some harm is sufficient to establish liability for all resultant harm, even if the extent or nature of the harm (such as psychiatric injury) was not specifically foreseeable. This underscores the breadth of the duty of care in negligence claims, particularly regarding pre-existing conditions.