1. Yes, the purchaser can still be required to complete, unless they then raise the longstop date. Essentially, both parties can by their conduct waive reliance upon a clause specifying a longstop date. However, there still is nothing to stop them then relying upon the longstop date, unless they have expressly agreed in writing to waive reliance upon the longstop date. In law both parties can treat the contract as continuing and subsisting if they wish. A right of election is given to each party whether to waive reliance upon the longstop date. Once there is an express election to waive reliance upon the longstop clause then the contract can go ahead. Here, so long as the purchaser by his conduct or agreement waives reliance upon the longstop clause, then he can be required to complete.
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