But the then-Fratton Park boss decided to overlook his inspirational midfielder’s Sporting Chance indiscretion to ensure it didn’t destroy the Blues’ promotion charge.
Merson was Pompey’s talismanic skipper during their memorable 2002-03 First Division title season which secured promotion to the Premier League.
However, in January 2003, Merson decided to take advantage of two blank weekends in their fixture list to seek help for gambling addiction.
He subsequently asked Redknapp’s permission to check into Tony Adams’ Sporting Chance Clinic for a week, a request which was granted.
However, Merson actually went on holiday to Barbados with his wife.
The game was up when he bumped into a friend of Redknapp’s while on an evening stroll along the seafront.
Yet despite learning the truth, Redknapp elected to take no action – and didn’t tell Merson he knew all about the lie until four years later.
The 75-year-old told The News: ‘I love Merse, he’s special to me, he will always be special, and I’m great friends with him now.
‘He’s had his issues and I probably treated him a bit differently to the rest of them, but they didn’t mind because he was special.
‘He was living in Birmingham so I’d bring him in for three days a week. I wouldn’t drag him in for the sake of a warm-down on a Monday. What’s the point of bringing him in for a 30-minute stretch, driving two-and-a-half hours?
‘Although there was that time when he was supposed to be recovering at Tony Adams’ clinic – and when he returned to us had the best suntan I’d ever seen.
‘It was so stupid. He’d been to Barbados and a mate of mine had seen him out there!
‘Although I knew and had the hump, I never did anything to him and never said anything.
‘If it had been anyone else, I would have booted them out, but I knew the only chance we had of getting promoted was with Merse.
‘I wasn’t going to stop the people of Portsmouth’s dream of getting promoted because I’d fallen out with him and kicked him out.
‘We couldn't get promoted without him, he was that good. He was our best player and ran the games.
‘Merse took a liberty with me, but I knew if I said “Clear off, you’ve had it” then we would have gone downhill. We wouldn’t have gone up.
‘I just wanted to get promoted that season, we all did. And we needed Merse.’
The following season they would claim the First Division title with a game to spare, amassing 98 points and 97 goals.
As for Merson, he netted 12 times in 48 outings for the Blues during what would be a first – and last – season at Fratton Park.
In July 2003, the former England man joined Walsall.
Redknapp added: ‘Merse told me: “I don’t think I can play in the Premier League, Harry”.
‘He had been there before and dropped down a league, now he was going back – and obviously knows the game inside out.
‘He said: “You’re going to need all hands on deck next year to try to stay up, you can’t afford a luxury like me who is only going to play when I’ve got the ball. You need everybody grafting”.
‘I had given him a free role when we won the title. He was fantastic.’
A message from the Editor, Mark Waldron
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