Parliamentary Voting System and Constituencies Bill

The Plant commission did not turn down AV. It said that it was a perfectly acceptable system, but that it just preferred another. That system was within the AV family of systems; namely, the supplementary vote. I know that the noble Lord has had to pick up the brief from others who unfortunately are not able to attend, but I am having difficulty in understanding why he does not accept the supplementary vote in his amendment. He alluded to it previously, but it was not clear to me exactly what he meant in his explanation. Will he tell us that before he sits down?