It had been suspected right through Sri Lanka's tour, but it is now official: Chandika Hathurusingha's knowledge of Bangladesh players and conditions provided Sri Lanka with a substantial edge.
Having been Bangladesh's head coach - a role he had held since 2014 - until October last year, Hathurusingha was instrumental to the long-term development of the Bangladesh side, and was privy to information on the state of individual players' games. His defection to Sri Lanka was acrimonious, particularly as he had not publicly divulged his reasons for the early exit. As a result, there has been rankling in Bangladesh about the insider information he has wielded on this tour. On the eve of Sri Lanka's final match in the country, Hathurusingha himself conceded his insight into the Bangladesh side had proved useful for Sri Lanka, who won the ODI tri-nation series, and the Test series.
"I think yes, to be honest [knowledge of Bangladesh did help]," he said. "We had some strategic plans for some of the players. We knew how they would react under pressure. They came very hard in the first two games, which I expected. If that didn't happen, I would have been very disappointed. I have never not left something behind. I was happy about it, and then happy about how we came back as well. All in all, it was a satisfying tour for me personally. But then again, after I leave, I want Bangladesh to do well. I am actually keeping [an] eye on how they are going forward."
Sri Lanka employed several unusual strategies throughout this tour, many of which yielded rich dividends. The emphasis on short-pitched bowling during the ODI tournament was almost certainly a strategy devised by Hathurusingha. Sri Lanka's reading of the two Test-match pitches was also near-perfect. In Chittagong, anticipating a batting track, Sri Lanka played an extra bowler. In Mirpur, which substantially favoured the bowlers, Sri Lanka handed a debut to Akila Dananjaya, who took the most wickets in the game. The offspinners also often bowled around the wicket to Bangladesh's left-hand batsmen - a ploy that was frequently effective.
Bangladesh's acting limited-overs captain was also of the view that some Sri Lanka tactics were founded upon Hathurusingha's familiarity with the opposition.
"Hathu was with us recently," Mahmudullah said. He knows pretty much everything about us. He definitely used that information. He is a quality coach, and he has the capability. But if we had done our job properly, we would have been winning and we wouldn't have had to talk about this. It was upon us to do something good."
Just as Mahmudullah placed blame for Bangladesh's performance on the team itself, Hathurusingha also suggested that at least some of the hosts' woes were of their own making. Bangladesh had dominated their first three matches of the tri-nations series, even inflicting a record defeat in their first match against Sri Lanka. But since then, they have been winless in five consecutive matches against Sri Lanka, across formats.
"I don't think Bangladesh panicked," Hathurusingha said. "They played really well at the start of the tri-series. They put both opposition teams under pressure playing how they know to play. I think they put doubt on themselves after few failures. I was surprised that they went down that quickly."
Having won the first match on Thursday, Sri Lanka cannot lose the T20 series, but they will sweep the trophies on this tour if they can muster another victory. After the torrid 2017 Sri Lanka had experienced, this tour has already been a substantial fillip to players and fans - much of the credit going to Hathurusingha's coaching.
"Actually I am very pleased with the response I got from the Sri Lanka players," Hathurusingha said. "I think it has got to do with the familiarity of being with my country. It helped me communicate better. It took time but they responded very well to the challenges."
Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando