Perhaps the 16 million + shares traded at the close on Friday had something to do with the TOLL / Virgin offer that went to Toll shareholders? :
As a TOLL shareholder, we received 1 VBA share for each TOLL one owned and were also given the option of buying more. Presumably some people took up that offer and that may explain the huge amount traded in (more or less) one hit?
I seem to recall the date it was to happen was the 22nd Aug.