London - Steve Waugh says the Ashes are too close to call as England and Australia prepare to resume battle, with the visitors seeking their first away win in the series for 18 years.
With the exception of the 2010/11 series in Australia, which England won 3-1, home advantage has been decisive since Waugh's side triumphed 4-1 away in 2001.
But the former Australia captain, 54, said it was "50-50" as to who would emerge triumphant over the course of the five Tests starting at Edgbaston on Thursday.
"I really believe it's a big ask for the fast bowlers on both sides to play five Tests in six weeks and that could have a big impact on the whole series, so for instance Jimmy Anderson gets injured, or Mitchell Starc gets injured for us, it could really affect the line-up.
"Depth in the squad will be important but I honestly think if I was a betting man I wouldn't back either side because I don't know who's going to win. It's going to be that even. I think it's going to be a fantastic series."
Waugh, who is mentoring the Australians, said it was a mystery why Australia had not won in England for so long but his advice to the players would be to "make your own history".
"We've come up against some really good England sides in those last 18 years. We've had some tight series and moments when we could have won the series, probably a bit like the other way round for England in that period where they lost a lot."
England go into the series buoyed by winning the World Cup for the first time - they beat 2015 champions Australia in the semi-final - but Waugh said that triumph would have no impact on the Ashes.
"One-day cricket is irrelevant to Test cricket," he said. "They're different teams, different captains. It's a different sport really. If you compare Test cricket and one-day cricket you're almost not playing the same sport. It's played in a totally different way.
"England will say it's important for everyone and sure, if you win that's great but when it comes to the first Test at Edgbaston it's not going to matter what happened in the one-day World Cup."
The first Test is taking place in Birmingham, where England have not lost since 2008, but Waugh said he would be telling his players to put that out of their minds.
"I've won there in Ashes contests," he said. "I think if you start believing something and building it up it becomes true but in my mind it shouldn't be an issue."
The former skipper, known for his uncompromising approach on the field, said he expected some rough treatment from English crowds for Steve Smith and Dave Warner.
The two batsman were each banned for 12 months over their involvement in a ball-tampering scandal in South Africa last year. Cameron Bancroft, also named in the Test squad, was banned for nine months.
But Waugh said Australia had turned a corner.
"Australia had to reset and revisit a few things, which is unfortunate because of what happened. I think they're in good shape. (Test captain) Tim Paine's done a really good job and he's a good leader. Hopefully you'll still see the Australian team play the Aussie way on the field.
"We've got to be combative and play in a positive frame of mind because that's the way we play our cricket."
He added: "Things culminated in Cape Town and were out of control there and there were a couple of ordinary series between different sides.... It did get to the point when it was over the top and something needed to be done so unfortunately for the guys involved they were the ones that paid the price.
"The good thing is now that everyone knows where the line is and you can't cross that line. It was great for kids too because kids all round the world saw that, particularly in Australia, and it was a good lesson as to what's right and wrong."