Having failed to find a new entrance on previous day (and narrowly avoided the thunderstorm mentioned elsewhere), we had to go in the usual way to finish the survey & derig. Did this, finding another 2 QM's & ignoring these as we had plenty to do then started mega derig with 2½ tacklebags, the drill, battery and ladder between us. Despite leaving the battery in Knossus for photos, it took 6hrs to get out - we were fucked. Also changed Strange Upfall rope for a long enough rope (45m) & staircase 36 one as it has been used for 3 years. Left 41m rope rigged on 3 Wise Men.