The next important stage is to analyse the contract illegal or not. In the case, Boron said that the rent book did not contain all the required information and he wanted avoid paying the rent. There was a case in the business law book which was related to this one. A landlord sued his tenant for arrears of rent amounting to $103 due in respect of a weekly tenancy. The tenant contended that the action must fail, since the rent book issued to him by the plaintiff did not contain all the information required by the Landlord and Tenant Act 1962. Such a default was punishable by a fine not exceeding $50. (Shaw v Groom) On the other hand, the Court of Appeal dismissed the contention. It was not illegal in its performance. From Sachs LJ’s point of view, although provision of a rent book was important, yet the contract did not illegal by statute. Therefore, in Boron and Helium’s case, although there was not whole information in the rent book, it could reflect that the contract may be not illegal in some respect. If innocent conduct was incidental to the performance of the illegal contract, its “incidental illegality” would not necessarily make it illegal and unenforceable. Because the two parties performed the rent contract for a period, the main parts could be valid. Helium should focus on the valid part to flight for her own rights and tried her best to enforce the contract in the normal manner to have the arrear of rent back. That was why Helium ought to ask for money instead of becoming very vulnerable to Boron’s defence.