Wickham denies that there is consideration for its promise to sell coal to Farmers'. Coal prices had risen significantly and Wickham wanted out of the contract to sell at a relatively low price to Farmers'.
There is consideration for Wickham's promise to sell coal to Farmers' only if Wickham gave its promise to sell in order to get Farmers' promises to buy coal if it wanted, and Farmers' gave its promise to buy in return for Wickham's promise.