This is where Warriors had to show their mettle and they did so in spades, combining street-smart game management with doughty defensive work. They could even have extended their lead during those 10 minutes with the 13 men – Dan Lancaster pushed a rare Glasgow penalty kick wide of the posts – but beyond that looked to have emerged unscathed until Clermont struck again when Irae Simone rounded off the final attack of the power play by crossing the line.

Harry Plummer’s conversion cut Glasgow’s lead to just five points but again they didn’t falter, instead continuing to take the approach that attack was the best form of defence. That paid off 10 minutes from time when Steyn crossed in the corner and this time Clermont had no response.

It will no doubt irk Smith that his team could go from having complete control to having to resort to firefighting mode just because of two needless yellow cards – Schickerling’s for illegally slowing down the game, Horne for a deliberate knock-on that led to the awarding of the penalty try – but there will also be a sense of pleasure at how his team coped in adversity, as Steyn noted.

“I can’t say what I was thinking when we got the two yellow cards as I’d be swearing,” he told Premier Sports. “We were obviously very nervous as you don’t want that. But we had a clear plan of what to do if something like that was going to happen. And I’m really proud of our forwards for the way they stepped up in those 10 minutes. We’ve just got a really good group that’s just really keen to play for each other.”

The first half couldn’t have gone much better, with Jones a revelation in what was his first outing of the season following Achilles surgery. His early surge out of defence eventually led to Clermont’s Pita Gus Sowakula being shown a yellow card for a deliberate knock-on as he tried to cut out Jamie Dobie’s pass to Scott Cummings.

Jones also claimed Warriors’ second try, scorching free of the Clermont defence after being fed by Lancaster, and then setting up the third with a smart kick that Clermont full-back Axel Guillaud couldn’t grasp. Kyle Rowe could scarcely believe his luck as he collected the loose ball and sent in Steyn to squeeze past the posts to score.

Steyn was also key to the first try in an unaccustomed role. Stuck into the front of the line-out, he cleanly collected Gregor Hiddleston’s delivery, dropped the ball off to Cummings for the maul to power over Euan Ferrie. Those three tries seemed to knock the stuffing out of Clermont but they finally bared their teeth when George Moala powered over from close range in a rare first-half attack.

That could have tested Glasgow’s nerve but they responded with a fourth try almost immediately, Horne taking the quick tap before the ball went through Jones and Rowe to Jack Dempsey who was never going to be denied once he got up to speed.

The second half was a more attritional affair following the two yellow cards and the penalty try but Glasgow expertly rode out the storm.The final try of the game owed a lot to Max Williamson who carried hard down the middle and then acted as de facto scrum-half to find Gregor Brown who sent Steyn strolling over in the corner.

Another maximum point win sees Glasgow into the last 16 with a game to spare to set up what could well be a shoot-out for top spot against Saracens at Scotstoun next Sunday. Steyn added: “Our goal will be to win again, especially being at home. Saracens are a really good outfit. They thrive on their rugby in Europe so we know it will be a good challenge. But we’re looking forward to playing them in front of our fans.”

Teams –

ASM Clermont Auvergne: A Guillaud, B Delguy (N Doornenbal 60), A Loaloa (I Simone 57), G Moala (T Frier 48), Y Fall, H Plummer, L Zamora; S Lotrian (E Falgoux 48 (S Lotrian 64 (G Dzmanashvili 70))), B Massa (S Lam 57), G Dzmanashvili (C Ojovan 48), T Lanen (L Michaux 57), R Simmons, K Tixeront, P-G Sowakula, S Tolofua (P Muarua 6)

Glasgow Warriors: K Rowe, K Steyn, H Jones (S McDowall 79), S Tuipulotu, J Dobie, D Lancaster, G Horne (B Afshar 74); P Schickerling, G Hiddleston (S Stephen 63), Z Fagerson (S Talakai 63), A Craig (G Brown 45), S Cummings, E Ferrie (R Sutherland 59 (M Williamson 63)), M Fagerson, J Dempsey (A Miller 73)

Referee: Luke Pearce (RFU)

Scorers –

Clermont: Tries: Moala, Penalty, Simone; Cons: Plummer 2

Glasgow: Tries: Ferrie, Jones, Steyn 2, Dempsey Cons: Horne 4

Scoring sequence (Clermont first): 0-5, 0-10, 0-12, 0-17, 0-19, 5-19, 7-19, 7-24, 7-26, (h-t), 14-26, 19-26, 21-26, 21-31, 21-33

Yellow cards:

Pita Gus Sowakula (Clermont – 6 mins)

Patrick Schickerling (Glasgow – 51 mins)

George Horne (Glasgow – 52 mins)