Il signor Mosson firma l'estensione del lease del suo appartamento per 190 anni. Ottimo. Peccato che le previsioni del ground rent indichino un iniziale e ragionevole pagamento annuo di £250, che duplicandosi ogni 10 anni arriva ad essere una somma annua di £1.3 bilioni.
La matematica é importante anche nelle clausole di un lease.
A leaseholder, Luke Mosson, signed a contract with his freeholder to extend the lease on his flat to 190 years. However, one of the clauses in the flat contained a term which said that the £250 ground rent would double every ten years. Luke Mosson bought a flat for £150,000, so a £250 ground rent per year would seem reasonable, and when he signed the contract he looked no further. But when it came to light he was shocked at what he had done. He calculated that if the ground rent doubled every ten years, over a 190 year period, the ground rent would be something like £1.3bn per annum.