The reasoning that lies behind the decision appears to be this:
1.All Wickham got in exchange for their promise to sell was Farmers' promise to buy if it wanted to.
2.Wickham did not give is promise to get Farmers' lack-of-any-genuine-commitment-promise to buy if it wants.
3.Therefore, there is no consideration for Wickham's promise to sell.
As we will see, the modern law holds there is consideration (by finding a genuine commitment that seller's like Wickham do get in return for their promise).
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