Section 20 of that Act (protection for interests of tenants at will etc.) shall apply with the modifications necessary to secure that persons with such interests as are mentioned in that section are compensated in a manner corresponding to that in which they would be compensated on a compulsory acquisition of that land, but taking into account only the extent (if any) of such interference with such an interest as is actually caused, or likely to be caused, by the exercise of the right in question.