Hold the celebrations: we haven't won the Ashes yet

Honestly, anyone would think we had won the Ashes series. I've done broadcasts on Australian radio and Indian TV today about England's win at Melbourne, while the story was leading all the British news items today. England retain the Ashes - but retaining is not the same as winning. We still lead by one with one match to play.

England have done marvellously well in winning two Tests in Australia for the first time since 1986 and by winning two by an innings for the first time since the series at home in 1985. Their win in Melbourne is the heaviest winning margin in the Ashes since Jim Laker did his spinning tricks in 1956. These are feats worthy of celebration, but the celebration should wait a week.

Delightful though it was to see the whole England team do the Sprinkler dance on the outfield after play, like the cast of The Full Monty only with the jockstraps under their whites, the job is not yet complete. They must avoid losing in Sydney next week to be sure of winning the Ashes. A 2-2 draw will seem like a mighty anticlimax.

If sport's version of Sod's Law works properly, Australia will call someone up for the last Test who they have ignored all series and they will make the difference in winning the match. Perhaps Nathan Hauritz will get a start on his home turf and take 16 wickets; maybe Usman Khawaja will make a double hundred on debut. This would take the gloss off England retaining the Ashes.

Andrew Strauss, the captain, is right to urge against complacency. It was not that long ago, after a heavy defeat in Perth, that people were writing that the wheels were coming off the Ashes wagon. What we have learnt is that Australia and England are remarkably inconsistent. The Melbourne party could be followed by a Sydney hangover.

If we were 2-0 up, I'd suggest that we could let Australia have one for morale's sake. It's what they often did with us, taking their feet off the jugular once the series was won. But England should have more ambition than a mere 2-2 shared series. A 2-1 win is the minimum requirement, 3-1 starts to look like a proper beating.

It could be argued that a 3-1 defeat would be in the best interests of Australian cricket too. Share the series and they can claim that basically everything is OK. But for some bad luck (like losing the toss at Melbourne), they would have won. I think this would be bunk, but Cricket Australia like all governing bodies will be looking for excuses rather than problems.

A 3-1 defeat means that Australia need to look at the coaching, the selection, the scheduling, the development. They need to go through rebuilding and perhaps jettison some members of the current set-up, and not just the players.

They need to confront the systemic failings that it took England several Ashes defeats to face up to. Then they may just be in a position to win the urn back in 2013.