Dubious bill from an expert

I would be grateful for comments on whether there are any fraud or money laundering concerns in the following situation.

As is usual in a fast track or multi-track civil dispute, a single joint expert was appointed to provide the Court with his expert evidence on the matter in dispute. His “expert” report contained many errors, all of which favoured the Defendants, and the Claimant successfully applied to the Court for permission to rely on the evidence of his own expert. The Claimant was a litigant-in-person at the time and did not realise that this changed the status of the single joint expert and he became the Defendants’ expert. The Claimant’s own expert, selected via the Internet, provided a report whose observations were either neutral or in favour of the Claimant. The two experts held a telephone meeting and produced their joint report, in which they concluded that they could not assist the court. The Claimant later succeeded in Court and was awarded his costs on the standard basis. Unfortunately, this usually means that he will receive only about 2/3 of his actual costs from the Defendants.

The Defendants’ expert (the former SJE), although experienced with court procedures, had still billed half of his fee for the experts’ joint meeting to the Claimant. The Claimant, being a litigant-in-person, assumed this was correct and paid it – as well as paying the full fee for his own expert. The Claimant only became aware of this error much later when the Defendants’ Solicitor referred to the change of status, whereupon the Claimant requested a refund of the half fee he had paid to the Defendants’ expert. The Defendants’ expert discussed the Claimant’s request with the Defendants’ Solicitor and then he refused on the grounds that the Claimant’s costs would be addressed by the Court and a refund would only complicate matters. The Defendants’ Solicitor and, almost certainly, the Defendants’ expert would know that only about 2/3 of his fee would usually be recovered by the Claimant. Thus, the total cost to the Defendants of losing the case would be reduced, even if not by a large amount.

The Claimant has been deprived of the expert’s fee for several years and is unlikely to recover all of it. If the expert does not refund his fee, then he does not gain (other than by avoiding the associated administrative tasks) but his clients, the Defendants, do gain.