Ashes finale a major test for England's progress, says captain Andrew Strauss

The final Ashes encounter is an acid test of England's ability to maintain their focus despite having already retained the famous urn, captain Andrew Strauss said on Sunday.

England retained the Ashes in Australia for the first time in 24 years with a crushing innings and 157-run win in Melbourne last week but Strauss again made it quite clear he did not consider the job done yet.

England, he admitted, had a habit of taking their eyes off the ball after successes, and letting the Australians level the series at 2-2 with victory in Sydney would be a huge disappointment.

"We didn't come out here to do that," Strauss told a news conference on the eve of the final Test at the Sydney Cricket Ground (SCG).

"In a good position to win a series like this, it's important we take it. It's a big challenge for us, a lot of people have been patting us on the back and telling us how brilliant we are. But the reality is you're only as good as your next game."

"Every Test is a test of the England side, this one in particular because the Ashes are coming home and it's easy to take your foot off the pedal and that's something I'm desperate to avoid," he added.

"It's a challenge for us and I'll be very disappointed if we don't deliver."

Strauss does not have to look too far back for an example of how England have followed a major victory with a disappointing result.

Comprehensive winners by an innings and 71 runs in the second test in Adelaide, England were routed by 267 runs in Perth in the third Test before turning things around again in Melbourne last week.

"If you look back at our record, we've been very good at coming back after defeats not to so good after wins. That's something we've got to put right," he said.

"Sometimes there are other reasons, sometimes the other teams play well, and sometimes we just weren't in the right place mentally."

"We've talked about it a lot, I think the guys are very conscious of it ... It's fairly simple, it's not getting ahead of yourself, starting a test match and not changing your gameplan just because you are ahead in the series."

Despite Strauss's obvious commitment to victory at the SCG, the tour would undoubtedly still be considered a success even if Australia were to win in Sydney.

For Strauss, though, captaining England is a longer term project and the fight against complacency will continue to the very end.

"We have made some achievements over the last couple of years, I think we've improved as a side in all forms of the game and we've still got further to go," he said.

"It's encouraging, you can take a lot of heart from the fact that we have been able to move forward as a side. We've got a pretty settled side and that bodes well.  

"But if we forget the formula that's got us to where we are, we're going to be in trouble."