Discusses the basic legal principles governing the granting of licenses to assign leases. Refers to two recent cases highlighting the problems encountered over the assigning of leases. In "Mount Eden Land Ltd v Towerstone Ltd" (ChD [2002] 31 EG 97(CS)) the judge held that, where the requirement for a surety is a precondition to the right to assign and is at the discretion of the landlord, there is no need for reasonableness. In this instance the landlord was reasonable in refusing to accept the guarantor. In contrast "London and Argyll Developments Ltd v Mount Cook Land Ltd" (ChD [2002] 50 EG 111(CS)) highlighted the principle that where insistence upon a surety is a condition of a consent that is required to be reasonable, the landlord can only rely upon written reasons given to the tenant at the time the condition is imposed. Principles set out in "Footwear Corporation Ltd v Amplight Ltd" (ChD Abs58921) concerning a refusal of consent should equally be applied to conditions imposed upon the giving of consent. The landlord's insistence upon a guarantor was not justified.