Read this: Regardless, the Luftwaffe could still inflict huge damage. With the German occupation of Western Europe, the intensification of submarine and air attack on Britain's sea communications was feared by the British. Such an event would have serious consequences on the future course of the war, should the Germans succeed. Liverpool and its port became an important destination for convoys heading through the Western Approaches from North America, bringing supplies and materials. The considerable rail network distributed to the rest of the country. Operations against Liverpool in the Liverpool Blitz were successful. Air attacks sank 39,126 long tons (39,754 t) of shipping, with another 111,601 long tons (113,392 t) damaged. Minister of Home Security Herbert Morrison was also worried morale was breaking, noting the defeatism expressed by civilians. Other sources point to half of the port's 144 berths rendered unusable, while cargo unloading capability was reduced by 75%. Roads and railways were blocked and ships could not leave harbour. On 8 May 1941, 57 ships were destroyed, sunk or damaged amounting to 80,000 long tons (81,000 t). Around 66,000 houses were destroyed, 77,000 people made homeless, and 1,900 people killed and 1,450 seriously hurt on one night. Operations against London up until May 1941 could also have a severe impact on morale. The populace of the port of Hull became 'trekkers', people who underwent a mass exodus from cities before, during, and after attacks. However, the attacks failed to knock out or damage railways, or port facilities for long, even in the Port of London, a target of many attacks. The Port of London in particular was an important target, bringing in one-third of overseas trade.
Now answer this question, if there is an answer (If it cannot be answered, return "unanswerable"): How much of the overseas trade did the Port of London take on?
one-third of overseas trade