Only certainty is that nothing is for certain

 European Cup pool-by-pool permutations: Even by the convoluted standards at this stage of the Heineken European Cup, the permutations in advance of the last weekend of pool matches are endless.

And if it is hard enough to understand, it's possibly just as hard to explain. But then this wouldn't be the European Cup if it were straightforward.

With only one team, Leinster, through to the quarter-finals, another dozen are genuinely in contention for the remaining knockout places. The six pool winners and two best placed runners-up will qualify for the last eight, with the top four at home, and victory for Leinster over Treviso will assure them a Lansdowne Road quarter-final.

Toulouse, Stade Français, Biarritz, Munster and Newcastle are next in line to win their pools and vie for a home quarter-final, but Leicester, Wasps, Northampton, Castres, Perpignan, the Dragons and Gloucester can all win their pools or qualify as one of the best runners-up.

With regard to teams finishing level on points in the same pool, their final placings will be determined by the number of match points from their pool meetings, and, failing that, the try tally and then the points tally from those head-to-heads.

As for ranking teams from different pools who finish with the same number of points, the deciding criteria will be the number of tries scored in all pool matches and, if that doesn't separate them, then it will come down to their respective points difference.

It is conceivable that a number of teams could finish on 19 points, (including all three in Pool One) although realistically the cut-off point for the best runners-up is likely to be 21 or 20 points.

With regard to procuring a home quarter-final, the threshold is more difficult to guess. More likely it could be as high as 22 or 23 points, although it could be as low as 19 or 20.

Basically, Munster need to win to get through, and could earn a "home" quarter-final at Lansdowne Road without a bonus point, although a five-point haul against Harlequins at Twickenham on Saturday would leave them very well placed.

If Munster win, without a bonus point, to obtain a home quarter-final they need two of the following three results to go their way - Wasps to deny Biarritz a win, Gloucester to beat Stade Français, and the Dragons to at least deny Newcastle a five-point haul.

If Munster win at Twickenham on Saturday with a bonus point, they need only one other result to go their way, namely Wasps to deny Biarritz a bonus point win, or Gloucester to deny Stade a win.

The three-way tussles in Pools One and Five throw up all manner of possibilities and conundrums. Ultimately, Leicester need a favour from their main English rivals, for a win by Wasps, without a bonus point, would leave the door ajar for Leicester to qualify with a five-point haul in Calvisano.

So Wasps, in what looks like being Warren Gatland's last season in Europe before returning to New Zealand, kick off at the Parc des Sports Aguilera knowing that beating Biarritz without getting a bonus point will most probably ensure Leicester's survival.

Talk about a dilemma.