The sub-lessee’s difficulty is that there is privity of estate between the freeholder and the head lessee, and between the head lessee and the sub-lessee, but not between the freeholder and the sub-lessee. However, the sub-lease may contain a covenant by which the head lessee covenants with the sub-lessee that he (the head lessee), will enforce the freeholder’s repairing obligations under the head lease. In that case, the sub-lessee can call on the head lessee to perform his covenant and enforce the freeholder’s