Answering as a lettings manager in an estate Agency......Obviously the Landlord is managing the property himself. The tenants (unless he has just bunged them in with no tenancy agreement) will have signed a contract. The Landlord can now serve them with a 'Section 21' notice, which gives them 2 months to vacate. You have enough evidence and the Landlord does not even have to give reason, unless thay are only at the beginning of the contract. Most tenancy agreements are for 6 months. For 6 months the tenant is locked in. After this time (unless the LL has asked them to sign again) it will go on to a 'rolling' tenancy, which means that if the tenant wants to leave they have to give one months' notice. If the LL wants them to leave he has to serve 2 months notice)