The short answer; highly unlikely. Unless the defendant can show they have ‘sufficient interest’ in ascertaining the ‘best interests’ of an incapacitated Claimant, which is separate to that of any financial interest.
In the case of RE SK (By His Litigation Friend, The Official Solicitor)  EWHC 1990 (COP) Mr Justice Bodey addressed the issue.
The case concerned a 55 year old man, SK, whom suffered a serious brain injury and physical injuries after he was hit by a bus in 2008. His brain damage was severe; to the extent that he lacked capacity to make almost all best interest decisions for himself. He required extensive rehabilitation and would require care for the rest of his life.
Judgement was entered in the Queen’s Bench Division (QBD) against the defendant bus company for damages to be assessed, subject to a deduction of 40% for contributory negligence. Prior to the completion of the civil proceedings, the local authority responsible for SK brought proceedings in the Court of Protection (COP) after SK had been removed from his placement by a woman with whom he had married (his capacity to enter that contract was also the subject of separate proceedings).
The proceedings in questions were brought to address the issue of where SK should be accommodated and cared for and the level of his rehabilitation regime.
During those proceeding the defendant made an application for joinder to be heard on those issues. That also included an application for the two sets of proceedings to be consolidated, or the issue of residence and rehabilitation to be preserved to the COP proceedingshe defendants primary concern being that the decision of the COP would bind them in the QBD as to quantum, which would put them at a disadvantage and create injustice.
In respect of the application for Joinder, Bodey J (applying the criteria in R73 and R75 COP Rules 2007) held that anyone wishing to be joined as a party must have ‘sufficient interest’. He interpreted this to mean an interest in the COP proceedings and therefore SK’s best interest. It was held this was distinct from any commercial interest.
In addition, it was held that joining the defendant would add nothing to the debate about SK’s best interest and therefore did not satisfy the criteria that their involvement is “…desirable to do so for the purpose of dealing with the application” (R73).
On the issue of crystallising the proceedings, Bodey J made clear that the decision of the COP is separate to the QBD and the two sets of proceedings addressed separate issues. He held:
“the key point in my view is that the underlying issue in the two sets of proceedings, however similar, is not the same. The jurisdiction of the Court of Protection is as to best interests and that of the Queen’s Bench is compensatory. The tests to be applied, although very similar (“best interests” as against “reasonable needs”) are not the same.”
This was supported by reference to the case of Sowden v Lodge  in which it was stated that “…there is a difference between what a Claimant can establish as reasonable in the circumstances and what a judge objectively concludes is in the best interests of the claimant”.
Bodey J made the points that the judge sitting in the QBD would make its own decision on reasonable needs based on the evidence before it in those proceedings. He went on to say that the QBD approach on quantum is a snapshot approach of the circumstances whilst the best interest approach was an ongoing and reviewable one. In particular he held:
“It is entirely foreseeable that there would be problems of increasingly costly and delayed decision-taking about the welfare of the incapacitated individual, if a Queen’s Bench defendant’s pecuniary interests were permitted to be locked into the best interests decision making process.”
As such, the defendants application for joinder was refused.
In comparison at the same time as the defendants application, SK’s brother made a separate application to be joined as a respondent to the proceedings. The brothers application was allowed on the basis he had ‘sufficient interest’ in the proceedings. Ultimately, the brother had an interest to ensure the best interest of SK were met and the best possible outcome was achieved for SK. That was not a financial one, which was essentially the difference between the defendants position and the brothers.