It transpires that thousands of flights were cancelled simply because of a mathematical model A glimmer of light has pierced the gloom, both literal and metaphorical, caused by the cloud of ash spewed skywards by the Icelandic volcano. From this morning, planes will be able to fly in the airspace above northern Britain. Since last Thursday, the entire country and much of northern Europe has been closed to air traffic, with potentially disastrous financial consequences for the airlines and causing severe inconvenience to millions stranded around the world. When this extraordinary event began, it was greeted as an example of...