The recent decision in 199 Knightsbridge Development Ltd v WSP UK Ltd provides a timely reminder on the different legal elements required to bring a successful professional negligence claim, including who must prove what. 

Knightsbridge concerned a professional negligence claim against a firm of mechanical & electrical engineers, WSP UK Ltd, in response to flooding damage caused by ruptures in the cold water system servicing the luxury residential development. The piping ruptured following an unexpectedly severe pressure surge caused when restarting the system pumps following an unexpected system shutdown.

The claimant alleged that WSP has been negligent because it failed to make enquiries with the manufacturer regarding measures to prevent such damage (which would have resulted in the providing newly developed anti-surge valves to be installed in the water system) and failed to provide instructions for a "slow refill procedure" to be placed on the control panel of the water system to prevent such severe pressure surges when the system was restarted following an unexpected shutdown.

The starting point in assessing the standard of care required in any professional negligence action is the standard of a reasonably competent professional within that field in that same situation i.e. the Bolam test.  Mr Justice Edwards-Stuart acknowledged that a party will not be held to be negligent if he acted in accordance with a practice accepted as proper by a responsible body of opinion in that particular profession.

Further, a party will not be held liable merely because another responsible body within the profession considers that the party is at fault.  However, if the exponents of the responsible body of opinion cannot demonstrate that the opinion has a logical or rational basis, the defence will not succeed. 

Likewise, if the reason why the chosen course of action was wrong was that the professional man (and others in his position) did not identify or foresee a particular risk, the Bolam test should not be applied.  For the accepted practice of a profession to be relevant, the responsible body must have first considered the relevant risk and then reached a logically defensible conclusion as to the cause of action required in response to it.  If not, the evidential onus will be on the defendant to show what he did and the reasons for it. 

In this case, WSP argued that it had not breached the required standard of care as the risk of damage caused by such a high-magnitude pressure surge was not one the profession as a whole generally considered in designing such water-systems. The court though held that the potential risk of such a severe pressure surge, although not anticipated by WSP, was not unforeseeable and fell within the scope of WSP's duty of care.  WSP had breached its duty of care in not implementing the necessary measures to protect against it. 

The claim though ultimately failed on issues relating to causation.  The court held that WSP's breach of duty was not the cause of the damage.  It reached this decision for two reasons.  First, the court held that, even though the manufacturer was aware of the application of anti-surge valves in residential developments over a year before the date the damage was caused, the Claimant had failed to prove that these would these would have been installed in the Knightsbridge water system before the damage took place.  This would have been the situation even if WSP had properly discharged its duty of care. Secondly, the court held that the Claimant had failed to provide sufficient evidence that WSP's advice to install the anti-surge valves within the water system and to conduct a slow-refill procedure in the event of an unexpected shutdown would have been followed, had it been given. 

In professional negligence cases it is often easy to find an error if you are looking for one.  Professionals are, by the nature of their work, open to such critique and the first target when something goes wrong.  However, this case is a good reminder that it is important to put all the pieces of the puzzle together.  It is not enough to find a mistake.  All the elements have to be present – duty, breach, causation and damage.  And more than that, the claimant (at least in the first instance) has to prove each of them.  If one is missing, the chain falls down and with it, the claim.