I would like to thank the following for their assistance:-

Prof.Felix Pirani for comments on the work in its current form, and Ross Turner for invaluable assistance in the tasks of writing the first draft, Brian Riddle and Arnold Nayler and for help in access to data, Gerry Lalor for advice about diagrams, John Wimpenny & Brian Kerry for discussion and information, Paul Dunlop, Ernst Schoberl, Mark Drela, John Langford, Martyn Pressnell, Nick Goodhart and Peer Frank for written information, Ron Moulton, Prof. Geoffrey Lilley, Frank Low, Jonathan Roper, Chloe Tahta & Bill Hetherington for helpful criticism, John McIntyre, Stuart Seymour and Malcolm  Whapshott for converting it for the web. and David Gordon Wilson for originally suggesting that I write it..