Brook’s position as skipper came into the spotlight after he admitted he was punched by a nightclub bouncer on a night out in Wellington, New Zealand late last year.
The 26-year-old was fined for the incident but it then came out that he was not honest about what happened in the investigation.
It was subsequently revealed that teammates Josh Tongue and Jacob Bethell had also been present when the incident occurred but Brook tried to protect them, according to McCullum.
“I think he was quite keen to put his hand up when the information came that it was going to land in the media,” McCullum said.
“He was hopeful that it had been dealt with internally, as we all were. He is a strong leader, he’s a young man, but he’s got a very good head on his shoulders and I know people will say he’s not that clever.
“I couldn’t disagree with that more. He wears his intelligence lightly and he’s a very strong leader, and he’s someone that they play for in their dressing-room as well, and our job is to just keep looking after him because he is still young.
“Brooky obviously was trying to protect his other players when he made that comment.”
McCullum also maintained that the England team did not go overboard with alcohol on the Ashes tour that followed the New Zealand trip, despite several videos emerging.
The England mentor added: “You have to be allowed to enjoy yourself as well. I don’t think the boys went overboard at all. In fact, I thought a lot of the pile-on for it was completely out of line.
“Are we trying to operate an environment which is guiding these guys, and nurturing them, and ensuring we put space between the times that things happen? Of course we are. It’s never changed.
“We care about these guys and we understand that they are still young, and our job is to try and nurture them through it. It doesn’t mean we’re going to get everything right either. There’s going to be times where we make mistakes.”
