MV Sea Tune is a general cargo ship of 1, 100 tonnes gross tonnage, 150m length overall and 20m beam with a summer draught of 9,2m. The engine is a 7 500 diesel with a service speed of 15 knots at a fuel consumption of 30 tons per day. Bunker capacity is 1750 tons. She is flying the Liberian flag and she is managed by a ship management company of Greece. On 12 April 2020 MV Sea Tune suffered an engine break down and breach of her hull during heavy weather off the coast of East London. Her port agents negotiated a towage contract with the East London port authorities to dispatch the port tug 'for the purpose of rendering any assistance the vessel may require'. The towage contract contained a clause which entitled the port authority to claim salvage. It read: 'The port authority shall, notwithstanding anything contained herein or any rule of law to the contrary, have the right to claim a reward for salvage, if the services rendered to the said vessel should be such as to warrant a salvage award.' The port was fully apprised of the disabled condition of the vessel. Pursuant to the towage agreement, the port authorities dispatched port tug Impunzi to go to the aid of MV Sea Tune. The port tug duly went out to MV Sea Tune, put a line across to her, and towed her to the port of East London for refuge. The ship was stabilised, her cargo and bunkers unloaded, and repairs begun. The port authorities claim that though the original contract was towage, the services they subsequently rendered are of such a nature that a salvage award is warranted. Advise the National Ports Authority's on whether in the circumstances of this case they are entitled to claim a salvage award or not? In your advice, elaborate lucidly on the circumstances under which a towage can be converted into salvage and thereby entitling the tug owners to claim a salvage award. Refer to relevant authorities.