G W Grace and Co Ltd v General Steam Navigation Co Ltd  1 All ER 201, per Devlin J at pp.206-207:
…the charterparty, either on its true construction or by implication, forbids the giving by the charterers of orders outside their powers, and, accordingly, that the giving of an order to sail to an unsafe port is a breach of the charterparty.
Once the breach of contract is established, it seems to me to follow that, subject to the ordinary rule of remoteness, damages must result. There may be cases in which the charterer is innocent of any intention to break the contract and where the master deliberately decides to enter a port which he knows to be unsafe. Roche J, on a rather similar point in Portsmouth Steamship Co v Liverpool Salvage Co (1929) 34 LlL Rep 459, indicated that the master should not follow the instructions of the charterer if they lead to obvious danger, but these factors go to the question of causation only. The giving of an order does not necessarily cause the damage that flows from an act done in pursuance of it. Put more specifically, the decision of the master to obey the order may in certain circumstances amount to a novus actus interveniens, but, in the circumstances of this case, the arbitrator clearly regarded the acts of the master as done in the ordinary course of things and not blameworthy. He was doing what any intelligent observer, knowing exactly how he was circumstanced, would have expected him to do.
Per Thomas J in Aegean Sea Traders Corporation v Repsol Petroleo SA (The Aegean Sea)  2 Lloyd’s Rep 39 at p.68:
… I do not think that one can conclude in general that a term as to safety will always be implied into voyage charter-parties where there is an unspecified range of ports. The issue as to whether a term should be implied as to safety and the extent of the obligation may turn on the specific terms of the charter.
Per Lord Justice Morris in Compania Naviera Maropan SA v Bowaters Lloyd Pulp and Paper Mills Ltd (The Stork),  2 QB 68, CA. at pp.104 and 105:
…Though there would have been a breach of contract in giving the order to go to an unsafe place, this would not justify the deliberate act of allowing the ship to suffer damage. The owners must not throw their ship away. If, having the opportunity to refrain from obeying the order, and having the knowledge that the ship had been wrongly directed to run into danger, those responsible for the ship allowed her to be damaged when they could have saved her, it would be contrary to reason if damages could be recovered. They could not be recovered for the reason that they would not be the result of the breach of contract, but of the deliberate and unnecessary act of those in control of the ship. Further, there is a duty to behave with ordinary reasonable prudence so as to minimize damages, and the readily attainable minimum may in some cases be nil. But this does not involve, nor in practice would it be reasonable or convenient, that where charterers have the contractual duty of ordering a ship to go to some place designated safe, and where the ship has the contractual duty of obeying the order, the ship must always doubt the validity of the order and must not proceed until, by making some reconnaissance or by seeking information extending beyond that ordinarily available to a reasonable and prudent ship’s master, there has been a satisfactory verification that a place designated safe is in fact so.
…If it were said that a port will not be safe unless, in the relevant period of time, the particular ship can reach it, use it and return from it without, in the absence of some abnormal occurrence, being exposed to danger which cannot be avoided by good navigation and seamanship, it would probably meet all circumstances as a broad statement of the law. Most, if not all, navigable rivers, channels, ports, harbours and berths have some dangers from tides, currents, swells, banks, bars or revetments. Such dangers are frequently minimized by lights, buoys, signals, warnings and other aids to navigation and can normally be met and overcome by proper navigation and handling of a vessel in accordance with good seamanship.
Per Lord Roskill in Kodros Shipping Corp v Empresa Cubana de Fletes (The Evia),  3 All ER 350 at p.360:
The charterer’s contractual promise must, I think relate to the characteristics of the port or place in question, and in my view, means that when the order is given that port or place is prospectively safe for the ship to get to, stay at, so far as necessary, and, in due course, leave. But if those characteristics are such as to make that port or place prospectively safe in this way, I cannot think that if, in spite of them, some unexpected and abnormal event thereafter suddenly occurs which creates conditions of unsafety where conditions of safety had previously existed and as a result the ship is delayed, damaged or destroyed that contractual promise extends to making the charterer liable for any resulting loss or damage, physical or financial. So to hold would make the charterer the insurer of such unexpected and abnormal risks which in my view should properly fall on the ship’s insurers under the policies of insurance the effecting of which is the owner’s responsibility…