This audio recording of David Lange's speech arguing the proposition that "Nuclear Weapons are Morally Indefensible" in the 1985 Oxford Union debate is used with the kind permission of Television New Zealand.
A full transcript of the speech appears online here and is published in Great New Zealand Argument: Ideas about ourselves, with an accompanying commentary by Margaret Pope, the author of the original speech notes.
Thanks are due to Karajoz Coffee Company for covering costs associated with this project, and CactusLab for their technical assistance and bandwidth.
EDIT: An hour of the debate, including the principal speeches, is now available on YouTube: