Deviation in the United Kingdom means geographical deviation. In the United States the concept has been extended to include other unjustified ways of carrying out the contract. The terms of the contract often give the shipowner the right to call at ports off the ordinary trade route. However, vague general terms will not be taken to confer a right to deviate. At times of oil crisis one will encounter a clause permitting deviation to obtain bunkers. Unless the charter party or bill of lading spells out the route to be followed, the carrier’s obligation is to follow the ‘customary’ or ‘usual’ route. This is presumed to be the direct geographical route, but the presumption may be rebutted by evidence of a practice actually adopted in a particular trade, or even by a particular shipping line. As with exclusion clauses, ‘liberty’ to deviate clauses will be construed contra proferentum i.e. against he who seeks to rely upon them. The question then arises as to what is the effect of unjustified deviation – for many years it was firmly held that deviation ‘goes to the root of the contract’, which lost the carriers the right to rely on an exclusion clause. The justification for such a strict view was at one time the equally strict view taken in insurance in that deviation in a voyage policy put the assured off risk as from the time of deviation. However, voyage policies today almost invariably contain a held covered clause which continues the cover in the event of deviation. Furthermore, the old strict rule of automatic termination for fundamental breach has been closely examined in the general law. It has been held inapplicable to intentional delays by the charterer. Deviation can however be waived. If the charterer continues with the charter after the deviation he cannot later change his mind and throw it up. Deviation remains a breach even if the charter party is not repudiated. The charterer will be entitled to foreseeable consequential losses but not losses that are too remote from the breach.