In the application of this Part of this Schedule in relation to an original tenancy which was a joint tenancy, a reference to the dwelling-house being the only or principal home of the ex-tenant is to be treated as a reference to the dwelling-house being the only or principal home of at least one of the ex-tenants of the joint tenancy.

The appropriate national authority may by order provide for this Part of this Schedule to apply in relation to an original tenancy which was a joint tenancy subject to such additional modifications as may be specified in the order.