150 The issues as to uncertainty raised by the defence are as follows. Firstly, it is said that cl 4 and par (a) of Schedule 2 of the 1984 agreement are uncertain and incapable of enforcement because it is uncertain what assets are comprised in the description of the Rhodes Ridge joint venture contained in the Schedule, particularly because of the history in relation to the changes in the form of the tenements and the gap in holding certain areas of land. I have discussed that above and I have said, for the reasons I have already given, that in my view, at any relevant time, when the 1984 agreement was made, when the option was exercised, and indeed now, the land comprised in the partnership interest in the Rhodes Ridge joint venture is readily ascertainable. I have expressed the view that, in my opinion, it matters not that the form of the tenements changed from time to time, given that at any relevant time the land the subject of the joint venture and the nature of the tenement was clearly ascertainable. It matters not, in my opinion, that some forms of tenement were created after the 1984 agreement was made. The time when it must be certain how the agreement is to be performed is not only the time when the agreement is made, but also the time when, using the mechanism provided by cl 4, it is, in the relevant respect, required to be performed.