"Oh, the flesh-eating beetles are in there," shrugs our guide, pointing to a locked door. This is the Darwin Centre, where a gruesome surprise lurks around every corner. The annexe to the Natural History Museum holds some 22 million biological specimens bottled up in jars - it's like walking into David Attenborough's Facebook account. Much of the collection is freely available to anyone who wants to see it, and is stored over eight floors,......