The parties’ agreement may be made in the course of written exchanges, e-mails, or during conversations and/or meetings, therefore so long as the parties have reached complete agreement, formal exchange of signed charterparty is unnecessary
Per Williams J in Behn v Burness (1863) 3 B & S 751 per at p.759:
Now the place of the ship at the date of the contract, where the ship is in foreign parts and is chartered to come to England, may be the only datum on which the charterer can found his calculations of the time of the ship’s arriving at the port of load. A statement is more or less important in proportion as the object of the contract more or less depends upon it. For most charters, considering winds, markets and dependent contracts, the time of a ship’s arrival to load is an essential fact, for the interest of the charterer. In the ordinary course of charters in general it would be so… Then, if the statement of the place of the ship is a substantive part of the contract, it seems to us that we ought to hold it to be a condition upon the principles above explained, unless we can find in the contract itself or the surrounding circumstances reason for thinking that the parties did not so intend.