It is the matchday bus rides to his new club’s stadium that, for Will Collier, perfectly capture the parallel universe of French club rugby. “You can hear the fans when you’re still a minute away,” says the former Harlequins prop, one of the latest band of Premiership pros to relocate to the Top 14, in his case to Castres. “You can see the smoke and the flares going off. There are drums and trumpeters … they even had a saxophonist last week. It’s absolutely bonkers. The passion is wild.”

Welcome to a different world. Castres, about 50 miles from Toulouse, is a modest-sized town of 50,000-odd people but rugby fever is rampant. “When we played Toulouse at home in October there were people crying in the pre-game guard of honour. It meant that much to them.” Despite the fact Collier played 240 first-team matches for Quins, last weekend’s atmosphere at Clermont’s Stade Marcel-Michelin also made the 33-year-old shake his experienced head. “I came back on following a yellow card and they were baying for blood. It was like they were at some kind of dogfight. It was a real cauldron … the energy from the crowd was unbelievable.”

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The genuine relish in Collier’s voice suggests the collective family decision to swap the easy familiarity of life in Putney for southern France has already justified the upheaval. No matter that, had he stayed, the popular and respected tighthead might conceivably have added to his two England caps. Better a bracingly fresh life experience than a nagging sense of “if only”.

Collier is far from the only former Premiership hired gun enjoying his change of scene. He, his wife, Kate, and their two young boys, Charlie and Freddie, enjoy meeting up on their days off with Jack Willis and his family, based in Toulouse. Former teammates such as Joe Marchant and Kyle Sinckler are at Stade Français and Toulon respectively while loads more exiled English internationals are scattered the length and breadth of France. Owen Farrell, Courtney Lawes, Mako and Billy Vunipola, Manu Tuilagi, Jack Nowell, Lewis Ludlam, David Ribbans, Sam Simmonds, Dan Robson, Kieran Brookes, Jack Maunder: the list is lengthy.

Which prompts the million-euro question, as this season’s Champions Cup commences: does the Rugby Football Union need to get with the beat and stop seeing all this as some kind of existential threat to the English game?

Might it not be good news in terms of broadening minds and developing character? And, perhaps, is this a timely moment to re-examine the rule decreeing that only players based in England are eligible for the national team?

That particular debate, from Collier’s perspective, is rapidly becoming a no-brainer.

“I don’t want to say, ‘Leave the Premiership,’ because the Premiership is a fantastic competition. For an older player who is still in the England mix it’s going to be very hard to make that call. But if you’re a younger player on the fringes I would certainly recommend it.

“Steve Borthwick has to be allowed to pick the best players he can. There’s the counterargument of: ‘We can’t weaken the Premiership,’ but I feel the Premiership is always going to be a great competition. It’s not like there’s going to be a huge exodus of players to France, especially with the Jiff rules [joueurs issus des filières de formation, which require a healthy percentage of locally-reared players in every Top 14 squad]. I feel quite honoured to have found a spot for myself in the Top 14 because they’re so hard to come by.”

Collier is equally convinced that a cross-fertilisation of ideas is beneficial for the English game, whether it be at international or club level. “South Africa are a good example. They benefit hugely from having players who have been all over the place and bring back different things from different rugby cultures. You also learn from different ways of coaching. In the Premiership it’s very often the same kind of rugby done in the same way.”

Venturing outside his comfort zone has also already taught him various other lessons. “Castres is a very small town but I’m absolutely loving it. Going away, experiencing a new culture … you have to grow. I’ve only been here for six months but you start to appreciate different things a little more. The pace of life is different, I’ve spent a lot more time with my family. I would 100% recommend it.”

As a partner in a restaurant in Bristol with some wine exams under his belt, Collier has also landed in his idea of gastronomic heaven. “Everything revolves around rugby and food, which just happen to be two of my big passions,” he says. “You can’t throw a stone without hitting a boulangerie here. You can also go down to the local supermarket and find the most incredible bottles of wine for €9-10 [roughly £8]. You think: ‘This can’t be good.’ Then you realise that back home it would be retailing for £30-40. It’s pretty amazing to have access to that kind of stuff – in limited quantities, obviously.” OK, but surely the family’s accommodation must be average? “We managed to find a beautiful house 15 minutes out of town with a big garden and a swimming pool. It’s got a chicken coop, four barbecues and a pizza oven. I’m a big barbecue fan, so it’s ideal.”

No further questions, your honour. Although, in mitigation, the big man’s day job of scrummaging against huge opponents every week is properly demanding – “There’s always something going on” – and there remains non-negotiable pressure to uphold civic pride at least once a fortnight.

“In the Top 14 it’s kind of unacceptable for us to lose a home game and that’s certainly the way we’re going to be treating it in Europe as well.”

It is also a frustration that Collier has a slight groin problem and is being rested for his side’s opening trip to Northampton on Saturday. Castres do not traditionally travel well in Europe but lazy perceptions are always ripe for challenging. “I think it is slightly changing,” says Collier, who will be back to face Munster at home next Friday. “There seems to be a real energy around the group to go hard this weekend.

“Every player has been coming up to me asking: ‘What’s it like at Franklin’s Gardens?’ It’s one of the things they want to tick off, playing against the English champions. We’ve got a big lumpy team with some star-studded backs so we’ll be sending a team who are capable of going toe-to-toe with Northampton.” Either way Collier and his fellow Francophiles do not sound particularly homesick.