So, the City of Winchester was the first and only merchant ship captured by the Konigsberg while she was cruising the Indian Ocean. Following her capture, the Konigsberg sank the British cruiser Pegasus, but was forced by mechanical issues and a lack of coal to seek shelter in the delta of the Rufiji, where she would be trapped and sunk by the Royal Navy. The only other German surface raider in the Indian Ocean in 1914 was the Emden. Emden operated mainly against coastal trade in and around the Bay of Bengal, and was far more successful. She captured or sank 18 ships, including the French destroyer Mousquet and Russian cruiser Zemchug. However, she would be sunk by HMAS Sydney following an attempted raid on the Cocos Islands.

The City of Winchester was a 6,600 ton ship, carrying general cargo (food, cloth and the like) on the route from Calcutta to the UK. She also carried the first of the seasonal Indian tea crop. Compared to Britain's consumption of tea, her cargo was a drop in a bucket. In 1904, the average consumption per person per week was 0.11 pounds. This comes to an annual consumption for the entire population of about 100,000 tons. As such, had City of Winchester's entire displacement been tea, that would have represented about 6% of Britain's tea consumption, not quite enough to cause shortages. As this required City of Winchester to be not just solely carrying tea, but to be constructed of it and propelled by burning it, it should be clear that her cargo represented a comparably small portion of Britain's tea import. More damaging to Britain's imports of tea was the freezes in shipping in the Indian Ocean that resulted from the depredations of the raiders. Emden's actions caused shipping in the Bay of Bengal to be halted between 14th September and the 2nd October. Similarly, Konigsberg's presence disrupted trade along the African coast and towards Suez in September and October 1914. This caused delays to tea imports in 1914, but did not continue into 1915 or later. Such hold-ups would certainly have had a drastic effect on the London Stock Exchange, but had no real lasting impact on tea supplies. As an illustration of this, by 1918, Britain's tea consumption was predicted to have increased to ~0.175 pounds per week per person, or about 160,000 tons a year for the whole population.

The first wave of German surface raiders was cleared from the seas by the end of 1914, with the exceptions of the auxiliary liners Kronprinz Wilhelm and Prinz Eitel Frederich. The former cruised mainly the Atlantic trade between America and the UK, while the latter mainly operated off South America's east coast. Another wave, this time mainly converted merchants rather than the cruisers and liners of the first wave, began operating in 1915-16. These had a mixture of targets, but only the Wolf entered the Indian Ocean. She had a successful cruise there, laying minefields off several major ports. Once again, she had little direct effect on the tea trade, but caused serious delays to shipping in the region. More effective at disrupting Britain's imports was the introduction of unrestricted submarine warfare in 1917. Over the course of the year, 3,729,786 tons of shipping were lost, just over two and a half times more than in any other year of the war. These significant losses caused supply failures for tea. This caused the Ministry of Food to introduce a uniform blend of teas from all available sources, which sold at 32 pence per pound from April 1918. Rationing was also introduced, with local rationing beginning in April 1918, and being extended to national registration in July. The ration was two ounces (0.125 lb) per person, It should be noted that, despite the best efforts of the Germans, that this ration was still higher than the average per capita consumption in 1904.

Sources:

The First World War and Working-Class Food Consumption in Britain, Ian Gazeley, Andrew Newell, IZA Discussion Paper No. 5297, November 2010

History of the Great War - The Merchant Navy, Volume 3, Archibald Hurd, John Murray, 1924

Review of German Cruiser Warfare 1914-1918, Admiralty, O.U. 6337 (40), 1940

SMS Königsberg, Pierre du Toit, The South African Military History Society, 2013