The language used by Robert in his letter to Emily was not sufficiently definite to constitute an offer; it was merely an invitation to treat. In Gibson v Manchester City Council [1979] 1 WLR 294, the House of Lords held that an indication of willingness to negotiate or an invitation to treat does not constitute an offer capable of acceptance. Robert's communication to Emily did not demonstrate a clear intention to be bound by the terms of a sale but rather indicated the possibility of negotiations. Therefore, there was no binding contract formed, and Emily cannot enforce the sale.

Key Point: In English contract law, a clear distinction is made between an offer and an invitation to treat. An offer must demonstrate a clear intention to be bound upon acceptance, whereas an invitation to treat is merely an indication of willingness to negotiate, which cannot form the basis of a binding contract. This principle ensures clarity in contractual negotiations and prevents parties from being bound by mere preliminary discussions.