They need to press this with the police because if this is fraud, then it is a police matter. If necessary, they need to make a formal complaint about the lack of action by the police bearing in mind they vehemently deny signing the transfer document.
It would be easy enough for the police to get a handwriting expert to verify whether this was their signature or not.
There is another issue here and that is that the solicitor dealt with this transfer is in breach of his duty to their clients who are the elderly couple and if he will not resolve this issue for them I suggest that they make a formal written complaint about the solicitors conduct to the Solicitors Regulation Authority who will investigate this very thoroughly.
Meanwhile, they need to make a formal complaint (it must come from them although you will of course be helping them with the wording) to the firm’s complaint to partner because the person dealt with this was under a duty to verify the identity of his clients and confirm that this was indeed their signature.
In conclusion, press the matter with the police.
Make a formal complaint to the solicitors complaints partner
Make a formal complaint to the Solicitors Regulation Authority if the firm of solicitors complaints partner does not come up with a satisfactory solution.
There is also the civil remedy of applying to court to get the transfer overturned on the basis that the transfer into joint names was done fraudulently. In 3 years the solicitor should have been on that case already.
There is another issue here and that is that if the solicitor that has been dealing with this for the last three years is the one who registered the transfer, there is a conflict of interest between what he wants and what is the best for the clients and therefore it should have been referred to independent solicitors to deal with. That forms a further head of complaint if it is the same firm.
Can I clarify anything for you?