Mr. Donal O'Raghallaigh:

I am sorry, as this is probably due to my explanation. Ignoring section 6.4 for the moment, the landlord can create security over the freehold interest. That security, or mortgage, is subject to the lease, so the lease has a higher priority than the security. The security just catches the freehold, not the leasehold interest where the entitlement to use, build and do everything is contained.