Eddie Jones’s all-or-nothing regime is designed to weed out England players who are not where they should be physically. Training is deliberately full-on, with 11 successive wins under Jones this year testimony to a more ruthless collective mindset. Even individuals recently sidelined by injury are expected to keep up or risk getting overtaken.

So it is hard to imagine just how determinedly George Kruis has had to graft to leap straight back into England’s squad for Saturday’s game against Argentina, having undergone ankle surgery only a month ago. For any big lineout-jumping forward, resilient ankles are an essential body part and to be preparing for a Test return a little over four weeks after an operation – the specialist initially warned it may take seven weeks – is remarkable. With Joe Launchbury now suspended, the race against time has paid off handsomely.

With Owen Farrell and Jonny May having also enjoyed near-instant success on their returns from long-term injuries, the conventional wisdom about needing a club game or two to rejoin the swing of things seems to have gone the way of half-time oranges. Kruis was determined from the outset to get back ahead of schedule and the conditioning staff at both Saracens and England have helped make it happen.

“We are in an environment now where you can push yourself in the weeks leading up to it as much as you can,” said Kruis. “Owen Farrell played [for Saracens] in Toulon – which was pretty much Test-match intensity – after having weeks off, but he still came back very sharp. Things like that give you a lot of confidence. If I didn’t feel right, I wouldn’t be here.”

Kruis even claims to feel better than before, having been bothered by a couple of floating pieces of bone in an ankle joint for the past year. It has not noticeably affected his performances but had begun to compromise his training ability. “There was a bit of wear and tear in the ankle. I’d been able to play on but more recently it’s been shutting it down a lot more. After the Toulon game last month I spoke to both parties [Saracens and England] and came up with the fact I needed to get it taken out as soon as possible. I want to be improving after every session, I want to do my extras, but before [the operation] I was struggling. I am really glad I’ve done it. I woke up two or three days after the op and thought: ‘It already feels better, the pressure in the foot feels less.’”

Given the 26-year-old has established himself as an ever-present for England in the second row alongside Maro Itoje, currently still sidelined, the prospect of a fitter, even more effective Kruis is one for all opponents to ponder.

The defence coach, Paul Gustard, knows him better than most, having coached lineouts at Saracens for eight years. “George is very tactically smart in terms of his lineout operation. I coached George and Steve Borthwick and I know the diligence and desire George brings to that area.

“He is enthused about lineout calling and gets excited about it. On top of that he is a very mobile, athletic player. The modern game is about athleticism and movement and if you can do that for 80 minutes in attack and defence, structured and unstructured situations, all the better.”

Kruis has not always been such an outstanding performer, having once been passed over by Harlequins for being too slight. “When I first saw him he was a skinny lad with a big nose,” Gustard said. “But you can see the muscle mass he has put on … he is now bordering 120kg. He’s a big kid. He has the bit between his teeth and wants to be the best he can be. As a modern-day professional athlete he is first-class. He has an internal drive to be the best.”

Nor did it do any harm that the young hopeful from Dorking RFC – who used to play with Elliot Daly’s brother – came up through the ranks at Saracens alongside a group of fellow aspirants Gustard now compares with Manchester United’s class of ’92. The Vunipola brothers, Farrell, Jamie George, Will Fraser, Jackson Wray and Ben Spencer have grown up together as professionals and both Saracens and, increasingly, England are reaping the benefits.

“People spoke about the class of ’92 at Man United, well Saracens had their own class,” said Gustard. “Once one started achieving there was enough peer pressure that they all wanted to outperform each other and strive to do things together. They are a close group.”

Kruis backs up that perception – “When you have five or six players coming through together it’s like the competition between brothers … it always pushes you a little bit further” – and believes there are a number of similarities in the way Saracens, the domestic and European champions, and England are now operating.

“If you look at results there are a lot of similarities as well. I think you’ve got to breed a culture in which people want to improve and constantly push each other. That’s what we’ve been doing.”

It now falls to Argentina to try to find a way around an increasingly formidable road block, with England apparently keen to shut down the Pumas’ sharply improved attacking game at source. “As a forward pack we’re definitely preparing for the physical, brutal challenge,” said Kruis, preparing to win his 19th cap. “We want to make Twickenham a horrible place to come as a forward.” He does not sound like an athlete about to tip-toe back into the fray.