Japan captain Michael Leitch knows England's new coach better than most and he has a stark warning for the players ahead of their first training session with Eddie Jones: "If you're caught slacking or you've not done your work, he'll come down on you like thunder and lightning."
In an interview with the Daily Mail, Leitch talks of being taken to breaking point by Jones but also of the encouragement the players take by seeing the growth and improvement they make under him.
Jones guided Japan to three wins in the World Cup pool stage and Leitch skippered them in their hugely impressive campaign and he warns England that they "might be in for a shock" when they encounter Jones for the first time.
"Eddie's somewhere between a devil and an angel," Leitch told the newspaper. "He works extremely hard and he's good at taking people with him. The mind-set definitely has to change if you want to keep up with him. If you're caught slacking or you've not done your work, he'll come down on you like thunder and lightning."
Jones will welcome England's Six Nations squad into camp on Sunday as they prepare for their opener against Scotland on February 6 and Leitch warns the players will have to take the rough with the smooth.
"There are times we would be up at 4am, then have several training sessions through the day and finish up our last meeting at 9pm," Leitch said. "I don't know anyone else in the world who works as hard as Eddie. He's known to manage on two or three hours' sleep for two or three weeks. If training was at 5am, he'd be there at 4am. It reaches a point where you think, "Holy s***, I don't know if I can do this", but once you start seeing the results you start to believe.
"Saying that, he would always allow time to have fun and go for a beer. He loves a joke. If he's cross at you on the training ground, he won't shut you out at dinner. He takes care of the boys if they're down, goes for a coffee and makes sure they're happy. He's fun to be around."