In Trustee Solutions and others v Dubery and another [2006] EWHC 1426 (Ch) (21 June 2006), the High Court held that documents issued by the principal employer of a final salary pension scheme, that purported to increase the normal retirement age for female members to 65, did not amount to a valid amendment of the scheme's rules. It was necessary for a document amending the rules to be signed by the trustees and employer, and the documents in question were not. There was also no effective estoppel created, as the evidence did not bear out the view that a common understanding arose that there was a normal retirement age of 65 for female members.