Hi, thanks very much for your question. My name's XXXXX XXXXX I'm going to assist you with it.
The solicitor would most likely be seeking the remedy of 'restitution' for the overpayment and, under English law, any negligence by the solicitor in making that overpayment will not provide you with a defence.
However, there are two defences that might well be relevant here. First, an overpaid beneficiary may be able to rely on the Limitation Act 1980 to prevent recovery where the payment was made over 6 years ago. This is because a claim for restitution is, in principle, subject to a six-year limitation period. The solicitors are likely to argue that (under s.32(1)(c) of the Limitation Act 1980) their claim is for "relief from the consequences of a mistake" and therefore the six-year period should not start until the mistake was discovered or should have been discovered. However, if they failed to exercise reasonable diligence in administering the estate, their recovery may still be limited by the Act. This will obviously be a matter of evidence.
Secondly, there is the defence of 'change of position'. Restitution essentially involves reversing the effects of unjust enrichment. Where the defendant has changed its position following receipt of the enrichment such that it would be inequitable to require it to make restitution, either in whole or in part, then the defendant will have a defence to a restitution claim. The courts have made clear that the application of this defence will be made on a case-by-case basis.
Hopefully this should provide you with a start to considering your options but if the sum is large it may be worth seeing a solicitor, even if just for an initial consultation (which may be free of charge or, at least, at a very preferential rate).
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