French heavyweights Toulon begin the defence of the European Cup at home to Glasgow this weekend in what is likely to be the last such tournament in the current format.

Leading clubs in England and France have served notice of their intention to quit the existing set-up when the agreement governing the running of the European Cup expires at the end of the season and set up their own separate competition, to which other teams from the continent have been invited.

Quite how the protracted debate over how next season will pan out might affect this season's competition is anyone's guess.

But it will surely add extra spice, especially from the Celtic and Italian sides, to a cut-throat tournament in which only the six pool winners and two best runners-up qualify for the lucrative knock-out phase.

Toulon's star-studded side, bolstered by the likes of Springbok Bryan Habana, All Black Ali Williams and proven match-winners Matt Giteau and Jonny Wilkinson are a match for any outfit on their day.

They host Glasgow, unbeaten in the Celtic League, on Sunday fresh from a 25-19 victory in the Top 14 over last season's beaten finalists Clermont.

Ex-Springbok flanker Joe van Niekerk, in his sixth season with Toulon, dismissed allegations that the Mourad Boudjallal-financed team were a bunch of mercenaries.

"I'm proud to say that this image is false," Van Niekerk told L'Equipe newspaper.

"People have seen that the boys play for their jersey, the town of Toulon, the fans.

"An Englishman, a South African, a Scot, all give their passion and their bodies for Toulon!"

Exeter and Cardiff complete Toulon's Pool 2, with the French club big favourites to advance.

Arguably the toughest draw was for Pool 1, pitching Top 14 champions Castres against in-form English giants Northampton, three-time winners Leinster and Ospreys, perennial underachievers in Europe.

Northampton travel to Castres and Saints coach Alex King, who spent six seasons at Clermont, admitted that they were under no illusions as to the challenge facing them.

"We've had three tough trips away in the Aviva Premiership and French teams at home are notoriously difficult to play," said King.

"We know what to expect. Castres are the French champions, they've got a very good pedigree and good players, and now we're looking forward to it.

"We want to win away from home. If you can win in France it sets you up very well in the pool, so that's been our focus this week."

Toulouse will likely battle Saracens to top Pool 3, and with minnows Connacht and Zebre making up the quartet, the first two both have a chance of progressing should they ramp up enough bonus points against the weaker opposition.

Last year's runners-up Clermont will have to disperse with the inconsistent run they have shown domestically if they are to have a fighting chance of safely negotiating Pool 4.

They face tricky matches against Jonny Sexton-fired French rivals Racing-Metro and rounded English outfit Harlequins. Scarlets make up the group, the Welsh region hoping to rebound from last season when it lost all six pool games.

Another humdinger is set for Pool 5, featuring three of last season's quarter-finalists in Ulster, two-time champions Leicester and in-form French club Montpellier, Treviso making up the numbers.

Ulster will be boosted by Ruan Pienaar's decision to stay put, but Leicester boast six British and irish Lions in their ranks, while Francois Trinh-Duc has been marshalling a Montpellier side that thrives on the up-front battle: certainly not a pool for the faint-hearted.

Pool 6 should be bossed by Irish province Munster, who will however be without retired metronomic fly-half Ronan O'Gara for this campaign.

They'll face opposition from Perpignan, Gloucester and Edinburgh.