Can I (as landlord of the property) go into the property without the permission of the tenant?
A landlord may be guilty of breaching covenants if they fail to meet their obligations contained in the lease such as breach of 'quiet enjoyment' (the tenant's right to live in and use the rented property without unwarranted interference from the landlord)
We would always advise that landlords gain the written permission of the tenant to enter premises. If landlords wish to do an inspection of a property, it is important that the landlord provides the tenant with notice of the inspection well before it takes place. If the tenant objects to the inspection then it cannot proceed.
Even if the agreement between the parties states that landlords can enter the property (for instance to inspect or show future prospective tenants around) these inspections can only proceed with the consent of the tenant.