For anyone considering this, note the terms and conditions. I have made bold the very important bit:
The Promotion commences at 00:01 am AEST on 31 July 2017 and ends at 11:59 pm AEST on 3 September 2017 (Promotion Period). Entry is open to members with a valid Velocity Frequent Flyer and valid flybuys membership account aged 18 years and over (Entrants). To enter the Promotion, Entrants must: a) successfully link their Velocity Frequent Flyer and flybuys accounts during the Promotion Period by visiting www.flybuys.com.au/velocity and completing the link process (Linking Entry Method).
The Promotion commences at 00:01 am AEST on 31 July 2017 and ends at 11:59 pm AEST on 3 September 2017 (Promotion Period). Entry is open to members with a valid Velocity Frequent Flyer and valid flybuys membership account aged 18 years and over (Entrants). To enter the Promotion, Entrants must: a) successfully link their Velocity Frequent Flyer and flybuys accounts during the Promotion Period by visiting www.flybuys.com.au/velocity and completing the link process (Linking Entry Method).