The meaning of words?

One appreciates the difference between a landlord requiring “a reasonable alternative guarantee” and its requiring “reasonable alternative security” for performance of tenant covenants. However, one might assume that the security referred to is of a third-party variety, or in the nature of a rent deposit. Yet, an assignee of a lease itself provides security, and, where a guarantor is seeking terms for a release, the covenant of the assignee alone could amount to "reasonable alternative security". So says the High Court in Landlord Protect Limited v St Anselm Development Company Limited [2008] EWHC 1582 (Ch). See http://www.bailii.org/ew/cases/EWHC/Ch/2008/1582.html