The dwelling-house was made available for occupation by the tenant (or a predecessor in title of his) while works were carried out on the dwelling-house which he previously occupied as his only or principal home and—
(a)the tenant (or predecessor) was a secure tenant of the other dwelling-house at the time when he ceased to occupy it as his home,
(b)the tenant (or predecessor) accepted the tenancy of the dwelling-house of which possession is sought on the understanding that he would give up occupation when, on completion of the works, the other dwelling-house was again available for occupation by him under a secure tenancy, and
(c)the works have been completed and the other dwelling-house is so available.