Possible to exclude postal rules

Holwell Securities Ltd v Hughes (1974)   On the 19 October 1971 Hughes granted an option to Holwell Securities to purchase a certain property for £45,000. Clause 2 of the agreement provided: 'THE said option shall be exercisable by notice in writing to Hughes at any time within six months from the date hereof...' On 14 April 1972 Holwell Securities' solicitors wrote to Hughes accepting his offer to sell his property. The letter accepting Hughes's offer was lost in the post.   
Q Had a contract been formed when the letter was posted on 14 April?   No.

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