In Farrar & Anor v Miller  EWCA Civ 295, the issue is whether a firm of solicitors which has been acting for a claimant in litigation pursuant to a damages-based agreement can validly take an assignment of their client’s cause of action.
It is the common law of champerty which militates against law firms acting ostentatiously as a party with a purely commercial interest in the litigation and it is their role as officers of the court which is cited as being core of the hesitation (see inter alia the EP study on third party litigation funding here). In England and Wales it was the rules against maintenance and champerty that, prior to 1990, led to solicitors ia not being able to conduct litigation pursuant to conditional fee agreements -CFAs.
Statute then intervened to change this in narrowly defined circumstances (CFAs and damages-based agreements only) however that did not lift the common law’s general opposition to same and it is this opposition which both the first instance judge and the Court of Appeal refer to to reject the possibility of assignment: 
the Assignment is neither a conditional fee agreement nor a damages-based agreement: what section 58(1) and section 58AA(2) show is that Parliament, being well aware of the common law rules, decided to go so far towards relaxing them as sections 58 and 58AA provide and no further.
Permission to appeal with the Supreme Court is being sought.