The Didymi 
The Didymi  2 Lloyd’s Rep 166 established the method by which a vessel’s performance should be assessed: A good weather method from which a vessel’s demonstrated performance shall be assessed across an entire voyage. The method envisaged by the Court is outlined as follows:
1. The vessel’s performance should be assessed in good weather conditions (generally Beaufort wind force 4 or below or as defined in the charterparty) on all sea passages from sea buoy to sea buoy excluding any slow steaming at charterers’ request.
2. If a variation of speed from the warranted charter party speed was shown, the variance should be applied with all necessary adjustments and extrapolated to all sea passages and in all weather conditions (excluding slow steaming at charterers’ request).
3. If a variation of fuel consumption from that warranted in the charterparty was shown the variation should be applied with the necessary adjustments and extrapolated to all sea passages and in all weather conditions (including slow steaming at charterers’ request).
Since “The Didymi” case was handled by the Court of Appeal, the principles from the ruling must be applied by all lower courts, including arbitration tribunals. There have been numerous arbitration awards that have made reference to the principles outlined by “The Didymi” ruling, thereby signifying the importance placed upon this fundamental Court ruling.
Additionally, there have been rulings from court cases such as “The Gas Enterprise” and “The Ocean Virgo” that have made reference to the well established principles explained by “The Didymi.”