Mark Clattenburg enjoyed a stellar career as a referee.
The Englishman became a Premier League referee in 2004 and he would hold that title for 13 years.
He was one of the best in the business during his career, being given the task of refereeing the Euro 2016 final and the Champions League that same year.
Clattenburg had to deal with hundreds of difficult characters during his time at the top of the game.
As we all know, being a referee is not an easy job. They are given abuse aplenty and Clattenburg would have been no exception.
But who were the most difficult players he had to manage during his time as a referee?
He revealed the five worst players he had to deal with during his career in an interview with Paddy Power back in 2019.
Goalkeepers are typically very vocal and one that wasn't shy in giving Clattenburg a piece of his mind was former Arsenal stopper, Lehmann.
"I used to find Jens Lehmann such hard work," he said, per the Sun. "He was always difficult because he’d always whinge about people stepping on his toes in the penalty area.
"A corner would come in and they would give him a little nudge and he’d go ballistic and push players and have arguments with referees."
Ferdinand is one of two former Man United players that make up the five.
"I found him difficult to referee during that Fergie era because he was always trying to play mind games," Clattenburg explained.
"He tried to get under your skin, probably to get that next decision. He was such a difficult player to referee as he was always in your face."
Pepe is the only player to have not played in the Premier League to make the list. His inclusion is not surprising.
"I had a run-in with Pepe in the Champions League final," he started.
"He was a guy who was always difficult because he’d try to frame stuff and wind attackers up to get them sent off, which is not always a great thing when you’re trying to referee a football match."
Keane is, without doubt, the least surprising player named.
"Roy was physical, hard and you couldn’t trust him," Clattenburg said. "Look at the tackle on Alf-Inge Haaland for example.
"You never knew what he was going to do next."
But none of them were as difficult to referee as former Newcastle ace, Bellamy.
Clattenburg explained: "The worst one - and I’ve thought it for years - was Bellamy. He was just the most irritating player on the pitch - and he was irritating off it.
"He was downright rude and it didn’t matter what you said to him.
"I made mistakes against him but what he used to say to you, it was not acceptable.
"He was a guy I just didn’t really get on well with."