In what circumstances will a solicitor be found liable for failing to advise a client of an onerous covenant in a lease?

In Sykes v. Midand Bank, [1971] 1 Q.B. 113 (C.A.), a solicitor had failed to advise his client of the existence of an onerous covenant in a lease that the client acquired. The client's subsequent action for breach of contract against the solicitor was dismissed on the ground that, as the client’s evidence did not exclude the possibility that he would have entered into the transaction if the solicitor had advised him of the existence of the covenant, no loss had been proven. The loss, in this case, would be measured by the value to the class members of the opportunity, if any, to decide whether to incur the fees. In these circumstances, I do not see any means by which - in accordance with section 24(1)(c) - the aggregate or any part of the defendant’s liability to any of the class members can reasonably be determined without proof on an individual basis. In consequence, I would reject proposed common issue # 4.