"Crikey, this bloke is a leader." That was what Paul Farbrace, then England's assistant coach, thought in October 2016 when Jos Buttler stood in for Eoin Morgan during an ODI series in Bangladesh, his first captaincy experience in senior cricket.
England, missing Morgan and Alex Hales due to their shared concerns about security, won the series 2-1 under Buttler's stewardship, overcoming a partisan home crowd and the heat and humidity to clinch the series in Chattogram after a win and a loss in Mirpur. But perhaps the most revealing moment came in defeat, when Buttler took exception to Bangladesh's exuberant celebrations after his dismissal.
"I think he showed the world that there is more to Jos Buttler than meets the eye," Farbrace tells ESPNcricinfo. "There's the quiet, nice image that the outside world sees but there's also a steely, driven, passionate bloke that people don't see. In that series, we saw that Jos Buttler has got teeth - and they're not just for smiling."
"I remember the press asking me about it," Buttler recalled on the High Performance Podcast this week. "I said, 'maybe you don't know me as well as you think you do.' That side to me doesn't get talked about as much [but] it's incredibly important. I really like that I have it.
"It's that determined, competitive side. The best thing you could do is come and watch me play warm-up football: I run around like Roy Keane, shouting at people and trying to hack people's legs. I do have a different side to me."
The Bangladesh tour represented the first three times Buttler captained his country, out of 14 in total: nine in ODIs, five in T20Is. Aside from that, he has only led two times at domestic level - both for Manchester Originals in the Hundred last summer - and has not been a regular captain since his days in Somerset's age-group teams.
But despite that inexperience, he has been groomed as Morgan's successor for more than seven years. Morgan personally picked him out as his vice-captain for the 2015 World Cup; he has briefly served in the same role under Joe Root in the Test set-up and is the incumbent at Rajasthan Royals.
For a number of years, younger players coming into the team have held Buttler in high esteem, seeing him as an example of what is expected at the highest level of the sport. "He leads by example in everything he does," Matt Parkinson says. "He's the best player in the world, isn't he? He's a freak in the gym, he's an unbelievable runner, he always trains so hard and hits loads of balls.
"Jos spoke up [after defeat in Dunedin] and said 'no, this is the way we need to keep playing', and Trevor [Bayliss] was very comfortable with that. Next game, we went to Christchurch for the decider and won
"He just keeps it really simple. The main thing is that he makes you feel good about yourself and your game, even if you're not feeling it or you've not had a good over. If you're one of his main bowlers, you'll always feel backed by him, even if you've had a bad day. He's very calm and doesn't let anything faze him."
During England's journey from no-hopers to world champions, Buttler made two telling off-field interventions which underlined his leadership role. The first came in a training session at Trent Bridge in 2016, the day before an ODI against Pakistan: boundary-riders were steadying themselves to throw the ball while balanced, but Buttler interrupted the session encouraging them to be more aggressive, picking up and throwing in one movement if they felt comfortable doing so.
The second came in Dunedin in 2018, the fourth ODI in England's five-match series against New Zealand. England had been 267 for 1 after 37.3 overs but collapsed to 335 for 9 and were beaten with three balls to spare thanks to Ross Taylor's 181 not out. Trevor Bayliss, England's coach, led the debrief, questioning whether the middle order had been reckless in their shot selection.
"Jos spoke up and said 'no, this is the way we need to keep playing'," Farbrace recalls, "and Trevor was very comfortable with that. The next game, we went to Christchurch for the decider, won the game, and it was immediately clear that the conversation in Dunedin had been a really important one."
In the Hundred, Buttler's challenge as captain was markedly different to the one he will face with England: bringing a squad of players together for the first time and helping them adjust to a new format with new regulations. He only played two games before linking up with England on Test duty, but he made a lasting impact.
"I'd come into the Hundred as a wildcard player and was really nervous," Fred Klaassen, a team-mate at Manchester Originals, recalls, "but he made me feel completely relaxed and backed me all the way. In the first game, he had a suggestion at the back end of the innings and rather than saying 'do this', it was more like 'what do you think of this?'
"That made it so much easier than having someone telling you exactly what to do. He empowered me and backed me 100%: he gave me that responsibility so that if I did fail, I failed on my own terms. Even in that short time, he demonstrated how calm he was as a captain."
After the third Netherlands-England ODI in Amstelveen last week, Klaassen felt comfortable approaching Buttler for some advice on a personal issue, despite having spent barely a week with him in the Hundred. "To me, Jos is an absolute gun and has that aura," Klaassen says, "but he also brings humility as well which was really refreshing."
Perhaps Buttler's greatest challenge will be managing his workload: he keeps wicket in both white-ball formats and looks set for a more regular role at No. 4 in ODI cricket in addition to opening the batting in England's T20I team. There is nothing in his career to date that suggests his form will drop off due to the additional burden: his ODI record is marginally better as captain, his T20I record marginally worse.
Buttler said after deputising for Morgan in the third ODI in the Netherlands - in which he made 86 not out off 64 balls - that it was important for him to "try and be myself" as captain. "I'm not Eoin," he said. "I can't try to be him, so I'll just have to - when I get to do it - try to be myself and be open to learning about it."
Matthew Mott, England's new white-ball coach, said that Buttler had "seamlessly transitioned" in that game after Morgan was ruled out by a groin injury; he will hope that the same is true about the full-time job.