<p>'However many times it has been done, the act of casting off the warps and letting go one's last hold of the shore at the start of a voyage has about it something solemn and irrevocable, like marriage, for better or for worse.'<br>Mostly Mischief's ordinary title belies four more extraordinary voyages made by H.W. 'Bill' Tilman covering almost 25,000 miles in both Arctic and Antarctic waters.<br>The first sees the pilot cutter Mischief re...