I have a property that I let through an letting agency in London.  The tenants came into the letting agency to make amendements to the agreement and sign.  They made the initial amendements and signed.  They have never received a completed final version of the agreement, nor have I.    I recently went to the property and saw that there where two dogs in the property.   I did not know that my tenants had two dogs.  When contacted about the dogs, the tenants claimed that the dogs where never a secret and made it very clear to the letting agent that they only saw places that allowed animals.   They claim that they attended a viewing of another property with the actual dogs and the letting agent was well aware of them.  Furthermore, when they signed the agreement, they made note to this effect on the agreement stating that dogs would be in the property.  Again, neither myself nor the tenants have ever received a completed signed agreement from the letting agency.  Hence, why I did not know about the animals in the property.  This is a complicated situation because I do not want dogs in the property but it seems that the tenants where always truthful with the agent about the dogs, even marking it in the contract.  What are my rights for ending the tenancy?  There is no break clause in the agreement.  Can I serve a notice 21 before March 2008 on the grounds that I do not want dogs in my property?  If so, what am I legally entitled to offer the tenants?  If not, do I have any other recourse?

Any advice please.