1258. Back-dated payment in respect of rent.

Where the new tenancy1 is granted after the original term date2, the terms of the new tenancy must provide that rent is to be payable at the rate ascertained in accordance with the statutory provisions3 with effect from the date of the grant of the new tenancy4; but, on the grant of the new tenancy, there is payable by the tenant5 to the landlord6 as an addition to the rent payable under the existing tenancy any amount by which for the period since the relevant time