CA 30 November 1998. Appellant (F) was granted a term of office premises for four years by a subunderlease which contained an option to acquire the subunderlessor`s reversionary interest at a max. price of £28,000. The reversionary interest was an underlease dated 29 January 1973 for a term of 40 years. The respondent (W) acquired the freehold in 1987 and the headlease in 1988, when W also became the registered proprietor of the underlease. In September 1988 F gave a notice to exercise the option to acquire the underlease. In proceedings by W seeking possession of the premises, and by F claiming specific performance of the contract arising on the exercise of the option, W asserted that, as the option had not been registered against its registered title to the underlease, it was not bound by the option, notwithstanding W`s actual knowledge of the option when it acquired the underlease. F appealed against the CC decision that W was not bound by the option. "Held" Appeal allowed.