The Parkhead captain was close to being shown the door by former manager Tony Mowbray during the 2009/10 campaign but Lennon was first-team coach at the time and offered him reassurance and encouragement. Then, when Lennon took over after Mowbray's dismissal, his man-management allowed Brown to flourish.
The first Brown knew of his boss's departure was when he picked up a newspaper last week, on the morning that it was later confirmed. Lennon had not contacted him in advance to tell him he was leaving, but they have spoken since the decision was announced. Brown won three league titles and two Scottish Cups during Lennon's four seasons in charge.
"It's been sad to see the manager go," he said. "Everyone was surprised. I think everyone was hoping he would stay and all of the lads enjoyed his training, along with Garry [Parker] and Johan [Mjallby]. He was amazing for me and helped me become the player I am. He turned me into a different player and I enjoyed my time under him.
"The manager understood where I was coming from, that I want to win every game and win every battle. He told me to pick and choose my battles, be more relaxed on the ball. At the time, Tony Mowbray was in and I didn't know whether I was going to be at Celtic or where I was going to be. I stayed strong and fought through it and the manager [Lennon] was brilliant. He turned me into the captain I am. I learned on and off the park from him and a manager you can talk to helps an awful lot.
"His biggest single quality was man-management. You could speak with him about anything and he knew he wasn't always right and I knew I wasn't always right in different situations. We came up with a plan. You always trust your manager and he puts faith into you. Gordon [Strachan] is exactly the same. You can speak to Gordon and Neil learned a lot from him."
Lennon and Strachan lasted almost exactly the same time as managers of Celtic; there were only six games of a difference in their longevity. The pair have always been close and Strachan, speaking at the Scotland squad's west London hotel ahead of tonight's friendly against Nigeria, spoke insightfully about Lennon's decision to leave.
"First of all, you've got to respect Neil's decision. That's all I can say because I've not spoken to Neil for a couple of months. I just know that at the end of nearly every season you go 'that's me, I've had enough'. And within two weeks you say 'we'll give it another bash'. Occasionally you go, 'no, I need a break'. If you can do the Celtic job, you can do most jobs in the world.
"You can reach a point in a job when you know it's time. I actually was like that at Coventry City. Before my final year, I went 'that's enough', but everybody convinced me to go back again: chairman, supporters . . . I knew that that was the most I could get from that group of players at that club. I had given my all and I really should have called it a day then.
"Did I ever regret leaving Celtic? No, I loved it! I wouldn't be here without having been there."
And there was no prospect of Strachan being invited to manage again by major shareholder Dermot Desmond, he said. "If Dermot phones me it will be for a game of golf, that'll be my lot . . ."
Celtic are in the process of identifying and recruiting Lennon's successor, of course, but Brown said the players would take on the responsibility of steering the club through their first ties in the Champions League second qualifying round on July 15/16 and 22/23 if the new manager was still finding his feet.
"We need to aim for the league again and the Champions League," he said. "We have to take a lot of responsibility. The new manager may come in and want to change the formation or change the ways, but we know what it is like to go through these group stages and that is what we have to try and focus on.
"Whoever comes in will be fine. It's a great job. It's not up to me. It's what the board decide and we have faith in them. It's huge for the club to qualify for that top tier of Europe and play the best teams in the world. For us to get in there is huge. The qualifiers are life and death for us and it makes the season a lot more exciting if you get into the group stages of the Champions League."