Clermont produced a simply sensational display as they taught Northampton a lesson with a 37-5 win at the Stade Marcel Michelin.
Two tries from Noa Nakaitaci, as well as scores Wesley Fofana and Nick Abendanon, helped Clermont to a thumping success as Saints never even threatened an upset.
Clermont came into the game fresh from a big defeat at Stade Français but they are a different side at home, and took just 40 minutes to tear Northampton to shreds.
While Saints stand ten points clear at the top of the Premiership, they have already been on the end of one hiding in the Champions Cup this season, and this was even more painful than their home defeat to Racing-Métro.
Outplayed in virtually every facet of the game, they missed far too many tackles and just couldn't live with a Clermont side producing some breathtaking rugby.
For all the talk of the stodgy nature of the Top 14, les Jaunards showed that there is still some creativity left, taking an improbable 27-0 lead in at the break.
The early scrum battle went the home side's way as Brock James knocked over the first penalty after four minutes, but that was the least of Northampton's problems.
A well-worked lineout move saw Fritz Lee burst through, and he fed Fofana on his shoulder with the France centre showing no ill-effects from the hamstring injury that kept him out of the end of the Six Nations.
While Saints got back in time to haul him down, the ball was spread wide, with Nakaitaci forced to check by the rush defence with two men outside him. With the pass not possible, he instead cut back inside, and slipped out of one tackle before bouncing over the line. The TMO was required to confirm the score, but he got it down, with James' conversion making it 10-0 after 12 minutes.
Stephen Myler then missed a long-range penalty for Saints, but they spent the rest of the half chasing shadows. Fofana and Abendanon were everywhere, with the full-back pirouetting out of two tackles before the ball came back for Fofana to sprint away.
On that occasion he lacked support, but Clermont soon stretched their lead with another James penalty after 25 minutes.
Abendanon then started the move that set up Clermont's second, collecting a high ball and breaking through. Fofana was on hand in support and ghosted straight past a huge attempted tackle from Courtney Lawes – the Saints lock would be withdrawn at half-time. Again Fofana couldn't go all the way, but the ball was quick, and James, playing in place of the injured Lopez, produced a lovely floated pass to send Nakaitaci over.
James converted from the touchline but Clermont still weren't done. Finally Fofana got over, turning up in support after Abendanon had skipped through the Saints backline, with James completing a magnificent first half with the extras.
The home side were first on the board in the second half, Sébastien Vahaamahina getting over the ball in the Saints 22 to earn a penalty in front of the posts. James took the easy three points as the lead was stretched to 30.
Northampton's afternoon went from bad to worse when they conceded a fourth try of the afternoon. They finally looked to be on the front foot, and Luther Burrell, who had endured a miserable time, almost broke through. He was stopped just short of the line but Saints were on the front foot. They tried to go through the backs, but Abendanon read the play perfectly, hit George Pisi man and ball, stripping it and sprinting 80 metres for the try.
It capped a brilliant display from Abendanon, who has enjoyed a cracking season since arriving in the Massif Central, making a mockery of the fact he has just two England caps to his name.
Julien Bonnaire blotted his copybook somewhat with a yellow card after playing Kahn Fotuali'i in a ruck, but even two men down, as Lee was getting treatment, Saints were held out. They looked sure to score when Christian Day was one-on-one with Abendanon but the full-back thumped the lock backwards.
They finally got over through Alex Waller with 66 minutes gone, although the Saints prop was lucky to stay on the pitch after John Lacey incomprehensibly ignored the unnecessary and ugly elbow he threw at John Ulugia's head after scoring which merited a red card.
It mattered little though, Northampton had been embarrassed, and the salt was well and truly rubbed in when Saints were marched back 15 metres off a scrum in the Clermont 22 with five minutes to go.
They will head to Saint-Etienne in a fortnight's time to welcome either Racing-Métro or Saracens, both of whom will hope to provide stiffer opposition. If Clermont play like this however, it's difficult to see anyone stopping them.
Tries: Nakaitaci 2, Fofana, Abendanon
Cons: James 4
Pens: James 3
Yellow Card: Bonnaire
Clermont: 15 Nick Abendanon, 14 Noa Nakaitaci, 13 Jonathan Davies, 12 Wesley Fofana, 11 Naipolioni Nalaga, 10 Brock James, 9 Ludovic Radoslavjevic, 8 Fritz Lee, 7 Julien Bonnaire, 6 Damien Chouly (c), 5 Sébastien Vahaamahina, 4 Jamie Cudmore, 3 Davit Zirakashvili, 2 Benjamin Kayser, 1 Vincent Debaty
Replacements: 16 John Ulugia, 17 Thomas Domingo, 18 Clément Ric, 19 Julien Pierre, 20 Julien Bardy, 21 Thierry Lacrampe, 22 Mike Delany, 23 Aurélien Rougerie
Northampton: 15 James Wilson, 14 Ken Pisi, 13 George Pisi, 12 Luther Burrell, 11 Jamie Elliott, 10 Stephen Myler, 9 Lee Dickson, 8 Sam Dickinson, 7 Calum Clark, 6 Tom Wood, 5 Courtney Lawes, 4 Samu Manoa, 3 Salesi Ma'afu, 2 Dylan Hartley (c), 1 Alex Corbisiero
Replacements: 16 Mikey Haywood, 17 Alex Waller, 18 Gareth Denman, 19 Christian Day, 20 Jonathan Fisher, 21 Kahn Fotuali'i, 22 Tom Stephenson, 23 Ah See Tuala
Venue: Stade Marcel Michelin, Clermont-Ferrand
Referee: John Lacey (Ireland)
Assistant referees: Leighton Hodges (Wales), David Wilkinson (Ireland)
TMO: Simon McDowell (Ireland)