Three, despite popular belief to the contrary, is not the magic number. At least, not when it comes to Test cricket.

Because Test matches played out over five days are even better when showcased in series of five matches.

And not just for neatness.

The five-Test series is an endangered species but remains the very best way to serve up the sport's greatest dish.

It's hard to imagine a finer advert for the merits of the five-Test series than the events of the last eight weeks.

In Australia, England were eventually able to make their clear superiority count with a commanding 3-1 Ashes triumph. Had it been a three-match series, then they would've still retained the urn, but with a vaguely underwhelming and unsatisfying 1-1 draw.

Such a result would also have allowed Australia to mask a host of deficiencies and, given what we now know, would've been a sporting disgrace.

Meanwhile, in South Africa, a truly magnificent but all-too brief series came to an abrupt end at 1-1 with the identity of the world's top side still in doubt.

Was there anyone, anywhere - South African, Indian or neutral - who upon watching the conclusion of the third Test at Cape Town thought "Finally, it's finished. Glad that's over"?

Cricket South Africa have made encouraging noises about future series against India being extended to four Tests - the same distance over which they have played England in recent times - and this is a welcome if insufficient step in the right direction.

The five-match Ashes series not only allowed England as a team to prove they were the better side but also gave individual players the chance to show their mettle.

For if Test cricket is the greatest examination of a player's technique, then a five-Test series is the greatest examination of a player's mind, stamina and fitness.

Rivalries develop. Players are 'worked out'. Plans devised, abandoned and rewritten.

In Australia, there were two standout batting performers: Mike Hussey and Alastair Cook. Hussey, placed under constant pressure by both his impressive opponents and misfiring team-mates, was able to sustain his form admirably for the first three games.

He hadn't failed to pass 50 in the first three clashes, the point at which most series come to an end. In the last two games, England were finally able to grind Hussey down along with his team-mates. He made just 53 runs in his last four innings.

Cook, meanwhile, was able to bounce back from a quiet game in Perth to confirm his staggering form with another stack of runs in Melbourne and Sydney.

Jacques Kallis and Sachin Tendulkar - and those watching in South Africa - were denied the opportunity to emulate Cook.

Indeed, the fact Tendulkar has just three five-Test campaigns on his record is perhaps the only black mark against an otherwise flawless career.

England's Ashes triumph has laid down a marker. While we knew Australia were no longer the world-beaters of old, only with convincing defeat in a full-length series was the depth of their struggles exposed.

It will be remembered that England landed the knockout blow to end the great Baggy Green era.

But Graeme Smith's South Africans in particular may wonder if they could have done so sooner had the opportunity been available.

There are a great many reasons why the Ashes is the greatest Test series in the world. It's increasingly rare - now almost unique - five-match duration is among the most compelling.