Hicks v Russell Jones & Walker [2007] EWCA Civ 844, [2007] All ER (D) 60 (Nov)
Rule 52.10(2)(b) of the Civil Procedure Rules (CPR) gives the Court of Appeal power to refer any claim or issue for determination by the lower court. Normally that is likely to arise where the appeal court has taken a view that a particular issue is necessary for decision, but that it could be better for it to be decided at first instance.
That may be on allowing an appeal, but the power is defined in sufficiently general terms to allow in a case where it appears to be just and convenient for a point to be referred back for determination by the lower court, even if it is only contingently relevant in the context of an appeal that is still pending.