Misrepresentation — silence / change of circumstances

In January, a doctor negotiating the sale of his medical practice tells the buyer, truthfully, that the practice generates around £2,000 a month in income. Contracts are not signed until May. Between January and May the doctor falls seriously ill, stops practising, and the patient list collapses, so that by the time of signing the practice earns almost nothing. The doctor says nothing about this change. The buyer, still relying on the January figure, completes the purchase and then discovers the true position.