Until a fortnight ago, most of us had never heard of Mali. Britain had no historical or trade links with this former French colony. Indeed, the idea that vital national interests were engaged there was too absurd to cross anyone’s mind. Yet today, the UK is being sucked ever deeper into West Africa’s volatile affairs, as the Government commits yet more men and money to a local war the Prime Minister admits could drag on for ‘decades’. ‘Mission creep’? This is more like mission explosion.