A professional person, be it doctor, lawyer, architect, engineer or quantity surveyor is not an insurer. In short he/she does not assume a risk for the client.
If the client wants that outcome, or relationship, the client should pay a premium to an insurance company, say, and await the future with equanimity.
What does a professional person do for a client, therefore?
In Eckersley v Binnie Partners (1988) 18 Con LR 1, Bingham LJ set it out as follows:
… a professional man should command the corpus of knowledge which forms part of the professional equipment of the ordinary member of his profession. He should not lag behind other ordinarily assiduous and intelligent members of his profession in knowledge of new advances, discoveries and developments in his field. He should be alert to the hazards and risks inherent in any professional task he undertakes to the extent that other ordinarily competent members of the profession would be alert. He must bring to any professional task he undertakes no less expertise, skill and care than other ordinarily competent members would bring but need bring no more. The standard is that of the reasonable average. The law does not require of a professional man that he be a paragon combining the qualities of polymath and prophet.
Many risks are not insurable against by the client, but one of the risks a client should not have to insure against is the negligence of, say a construction professional. Indeed, to do so may be a bad idea; it implies that, as between them, the client is bearing the risk. In addition, if the client and the professional are the named beneficiaries of the policy, the client will no longer have a right of action against the professional (Petrofina (UK) Ltd. v Magnaload Ltd.  QB 127)
NOTE: UK case law is of significant persuasive value in Ireland but is not, of course, conclusive on any legal question here.
NOTE: Bingham L. J. seemingly failed to recognise that professionals can be female.