Where the tenant of a dwelling-house has sub-let a part but not the whole of the dwelling-house, then, as against his landlord or any superior landlord, no part of the dwelling-house shall be treated as excluded from being a dwelling-house let on an assured tenancy by reason only that the terms on which any person claiming under the tenant holds any part of the dwelling-house include the use of accommodation in common with other persons.

Nothing in this section affects the rights against, and liabilities to, each other of the tenant and any person claiming under him, or of any two such persons.