At last Hong Kong and Taiwan are helping to stimulate the Japanese economy. Diaoyu activist Tsang Kin-shing and his fellow Hong Kong protesters may not be aware of their beneficial effect on Japan. And their hotheaded colleagues from Taiwan have probably thought even less about it. But in more economically literate circles - such as the elite readership of this column - it must be blindingly obvious. The Taiwanese convoy heading for the disputed islands has announced it will be armed with crossbows 'for defence'. Taipei county councillor Chin Chieh-shou said the bolts might even be tipped with explosives. There would also be a secret weapon, which would hurt but not kill. Now let us, for an unpatriotic moment, put ourselves in the shoes of the Japanese. What happens when foreigners threaten to invade what you regard as your territory from the sea? Why, you beef up your naval defences. When they come armed with weapons not seen in naval warfare for 500 years, your defence industry goes into overdrive. And what does that do to the average industrial economy? It stimulates domestic demand and provides jobs. Urgent research into a new hi-tech anti-crossbow shield means employment for weapons scientists. Idle production lines start building Senkaku anti-bolt missiles and Takeshima fishing-smack torpedoes. Nations like South Korea will breathe a sigh of relief at the strengthening of the yen. Imagine the profits to be made selling crossbows to Japan's rivals. Imagine the sighs of relief from cash-strapped defence ministries as they realise the arms race can be won with a few extra divisions of bowmen in medieval armour. So much more twang for your buck than nuclear weapons. True, nervous investors might rush to the US dollar for cover. But that would be temporary. Everyone would see Japanese fundamentals were now sound. But does the Hong Kong contingent really want to raise regional tensions or get themselves killed in the crossfire? Mr Tsang and the Hong Kong team due to set sail to the Diaoyu Islands tomorrow promise their demonstration will be peaceful. We should be grateful for small mercies. Mr Tsang is fearsome enough girded only in moral outrage, without having his unlicensed finger on any triggers. But in the heat of the moment, can we be sure the Japanese navy will be able to tell the difference between the armed Chinese in the Taiwanese flotilla and the unarmed Chinese in the single boatload from Hong Kong? Let's all calm down now, boys, OK? Before someone gets hurt.