The document issued by Heathrow [
http://www.heathrow.com/file_source/...ach_trial.pdf] is a very poorly-scribed piece of work indeed, peppered with errors in both grammar and syntax, and does not to my mind represent the (hopefully) more clear thinking behind the project. It's a shame that Heathrow could not apparently run to the expense of having a literate person proof-read the document prior to publishing it. End of rant - back to mowing the grass.