JUDGMENT:

Lady Justice Arden:

[1] This is an appeal by Singapore Airlines Ltd ("SA") from the order of Peter Smith J dated 20 January 2011. It raises important points about the meaning of "Earnings" for the purposes of The Singapore Airlines Pension and Life Assurance Scheme ("the Scheme") established by SA for its employees. The expression "Earnings" plays a key role in determining the amount of an employee's pensionable earnings and the amount of his or her contribution to the Scheme. The judge's order was made on a preliminary issue in a claim brought by SA in proceedings against the respondent, Buck Consultants Ltd ("BC") for negligence in the drafting of a revised version of the rules of the Scheme in 2000. We are not concerned with those allegations in those proceedings save to note that the preliminary issue had to be resolved for the purposes of SA's action against BC. However, and this is relevant to an issue as to costs considered below (Issue 4), BC had also been appointed by order of the court to represent the members of the Scheme on the preliminary issue.

[2] The Scheme was established by an interim trust deed made on 28 June 1974. SA is, and at all material times has be