There is a new form to apply to keep a pet in your home.  Section 3(7) of your Tenancy Agreement says you are:

“Not to keep any pets without first obtaining the written consent of the Landlord which will not be unreasonably withheld but which may be conditional.

Such consent may be revoked at any time if, in the opinion of the Landlord, any pet kept by the Tenant on the Premises is likely to cause a nuisance or injury to any other tenant, member of his/her household, visitors or neighbours, agent or employee of the Landlord.”

You can find the form here.