The landlord cannot be liable for this action of the tenant.

However, under section 8 of The Misuse of Drugs Act 1971 the landlord must not “permit” such activities to continue. This means you must now take some action against the tenant to ensure the activities cease. This would be a section 21 – 2 months – notice.

8 Occupiers etc. of premises to be punishable for permitting certain activities to take place there.

A person commits an offence if, being the occupier or concerned in the management of any premises, he knowingly permits or suffers any of the following activities to take place on those premises, that is to say—

(a)producing or attempting to produce a controlled drug in contravention of section 4(1) of this Act;

(b)supplying or attempting to supply a controlled drug to another in contravention of section 4(1) of this Act, or offering to supply a controlled drug to another in contravention of section 4(1);

(c)preparing opium for smoking;

(d)smoking cannabis, cannabis resin or prepared opium.