P was physically handed a letter detailing D’s offer to sell him land. D then posted a letter revoking the offer. After the revocation letter was posted, but BEFORE it arrived at his house, P posted an acceptance letter. CA held that a revocation letter only has effect once it is communicated, whereas an acceptance letter has effect once it is posted. Therefore the contract was valid because revocation was too late. The rule that acceptance letters are effective from being posted applies where it MUST have been “within the contemplation of the parties that, according to the ordinary usages of mankind, the post might be used as a means of communicating the acceptance of it”-Lord Herschell (he bases this on precedent, NOT policy reasons). In this case acceptance by post was in contemplation since the parties lived in different towns.