The theory of just compensation is that the dispossessed owner is no worse off after the compulsory taking of his/her land or part of his/her land, than before the compulsory taking. Lord Moulton expressed the concept in the PFA case as follows:

Probably the most practical form in which the matter can be put is that they were entitled to that which a prudent man in their position would have been willing to give for the land sooner than fail to obtain it.

Old legislation generally, required the assessment of the "value" of the land taken. The various heads that make up Special Value to the Owner were implied and developed by the courts over time. However, modern legislation lists the heads of compensation, for example; s55 of the Land Acquisition Act (NSW) 1991. The "value of land" test was abandoned in the UK in 1919 after investigation of the resumption process in the Scott Report. It has also been abandoned in Canada, South Australia, NSW and the Northern Territory.