Casting my mind back over the English defeats I have witnessed in Australia,
the last trip four years ago
must go down as the worst of the lot, which makes this result all the more special.
Many of us saw the 5-0 reverse coming in 2006/7. We felt the hard work had not been done and there was no excuse for that. We knew how Australia would respond to their 2005 loss, we knew what sort of bulldozer would hit England in Brisbane.
For some reason, England did not see it coming, they had no idea, no preparation at all. It was a totally unprofessional tour. The wives and girlfriends were out there from the start. There was no proper focus. It was a stinker.
Many of the other tours left me with a similar feeling. I would crawl into the commentary box of Australia's ABC radio to apologise and make excuses for what was going on in the middle. It was embarrassing and my Australian colleagues would have a good laugh.
But this time the boot is on the other foot and, to be fair, the Aussies have taken it really well. Hopefully they realise it is actually good for them to have lost the Ashes.
They will hate to admit it but they have got so many issues within Australian cricket that need addressing and it is a defeat like this that brings those matters to a head.
It means administrators and selectors have to take action rather than only think about taking action.
Victory ends 'shame and embarrassment' for Agnew
A good old defeat does not do anybody any harm and the Australia fans will be out in force when England return in 2013/14, desperate to see their side win the Ashes on home soil. This result breathes new life into one of sport's greatest rivalries.
Meanwhile, the travelling supporters will be celebrating for some time to come. To put it into context, the last time England won in Australia the Barmy Army had not even been formed!
They first appeared on the scene in 1994.
That is five tours in which they have paid all that money, spent all that time, chanted all those songs and drunk all those beers without seeing England win. Twenty-four years since the last success is a very long time.
I am not sure the players fully appreciate the magnitude of their achievement. During the tour, they have been so focused on the here and now that they have not had the chance to look ahead.
They would have walked out on Wednesday thinking:' 'Let's finish them off'. Suddenly - bang - it has happened and now they will be asking themselves: 'What do we do? How does it feel?'
The attitude and spirit within the squad has been spot on.
I am extremely lucky to deal with the players an awful lot and they are genuinely very nice lads. Character, maturity, friendship - this team exudes all of that and a lot more.
Team director Andy Flower again showed himself to be an outstanding coach and a superb dealer of people
But the key to their success was preparation. It was hopeless in 2006 but this time round they have used it really well, there was no messing about. It generated team spirit and brought players into form.
Team director Andy Flower again showed himself to be an outstanding coach and a superb manager of people. He and captain Andrew Strauss complement each other very well.
Strauss is very much respected and liked by his team-mates. He has had a very good series as far as the captaincy is concerned, He has made lots of good decisions and enjoyed a spot of luck here and there.
The backroom staff have had a massive impact. They are incredibly dedicated people, very clever, innovative and always looking to improve. They want England to be number one.
People raised their eyebrows when Richard Halsall was appointed as fielding coach but just look at the results. England's fielding has so much better than Australia's - and that has not been the case for 20 years. We used to laugh at Phil Tufnell letting the ball through his legs down in the deep!
It is now Australia who have to go away, look at what England do and try to emulate them in order to improve and catch up with us. That is new territory.
For the last 20 years, we have had all this talk about needing an academy because Australia have got one, needing to reduce the number of first-class teams we have got because Australia have not got so many etc.
Well, now it is us doing things right and certainly the investment in our coaching staff has paid dividends.
But the series is not over yet. On we go to Sydney for the fifth and final Test. Will England win the Ashes? At the start,
I predicted they would win 3-1.
I am pretty confident that will still be the case.
Jonathan Agnew was speaking to BBC Sport's David Ornstein.
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