One cannot rule out the possibility that this game might end today itself. Having allowed Australia to score a massive 481, England then suffered a severe collapse and ended the second day with 107/8 on the board. To add insult to injury, they are 374 runs behind Australia's first innings total and look highly vulnerable against the touring bowlers. With just two wickets in hand and 175 more needed to avoid the follow-on, one can safely assume that England may have to bat again...very soon.
The Ashes, 2015: Live Cricket Score of England vs Australia, 5th Test, Day 3

The question remains - how long can they delay the inevitable....
For the first time ever Michael Clarke has enforced follow-on in his Test career. And he does it in his final Test match!
Moeen Ali and Mark Wood began day 3 with intent to defy the Australian bowlers as long as possible and they did it comfortably for a while. They played with ease that was absent in the top-order and soon brought up a half-century stand for the ninth wicket.
However, one cannot blame them for the lapse in concentration and with the form the Australian bowlers have been in this match so far, it was only time before they bowled England out. Johnson picked up Wood and Moeen on back-to-back deliveries. Wood miscued the pull to mid-wicket and then Moeen nicked one to the keeper.
England trail by 332 runs and with almost three full days left, it looks highly unlikely they might be able to save this....