Powell described himself as one of a number of “facilitators” who had been there to “shape and support” the player on his journey.
“You could see cricket was in his blood, cricket was part of his family,” he said.
He believes Bethell honed his batting ability while facing taller opponents in Barbados.
“Most of the deliveries he faced were in his upper half,” he said. “So he had to develop a way to cope with that, which he did naturally because that’s all he faced.
“That’s been telling this week because he dealt with that. He plays that really well.
“Once you’ve got that and that belief that you can cope with the most dangerous weapon a fast bowler has, then you can deal with the rest of it.
“It’s been a very special week in the Bethell household and I think we’ve all seen live what it’s meant to Jacob himself out in the middle and also his family.”
Bethell is now the fifth man to score his first first-class hundred in a Test for England.