Look: Federer fans mourn exit of the 'gentleman of tennis'

"The gentleman of tennis." "A tennis god." Roger Federer is preparing to leave the stage for the final time and fans cannot bear to see him go.

The Swiss maestro, 41, will play his last match when he teams up with long-time rival Rafael Nadal for a doubles match at the Laver Cup in London on Friday.

As so often in his illustrious career, which has spanned nearly a quarter of a century, he is once again the main attraction at the O2 arena, where Team Europe will take on Team World.

Thousands of paying fans queued up even to watch Thursday's practice sessions on the eve of the three-day tournament.

Judith Flavel, 68, who is retired, was wearing a red T-shirt with a cross made up of Federer's name in white, echoing the Swiss flag.

"He's the best," she said. "I know the argument about who is the best of all time and that can be any of the three (Federer, Nadal, Novak Djokovic), depending on which criteria you use, but to me he's the gentleman of tennis.

"Nadal is close, but his (Federer's) sportsmanship, his work ethic -- I like everything about him.

"They've been talking about his retirement for the last 10 years. It's never time but it had to come sooner or later."

Naia Martin, 27, who works in human relations in London, was waiting in line in a green Federer cap, flagging her allegiance to the 20-time Grand Slam champion.

"I've kind of actually dreaded this day," she said. "It sounds very serious but it's true. I've just always loved watching him play.

"Not just his tennis but how he holds himself on tour. He's a true gentleman. Watching him at Wimbledon is amazing. He's perfectly fitting for that place, the prestige.

"I think the dominance that he had was great. Obviously we've seen dominance from other players as well, but for me no one will compare and it will be a struggle to find someone I will support as much."

Salma Mashhour, 30, a PhD student from Egypt, who lives in London, snapped up tickets for the practice session as soon as they became available.

"We bought the tickets the very same day at the very first hour they were released, back in March, because they said Federer was going to be there, so it's always been about him," she said.

"I'm excited," he said. "I like the way he plays and have got inspiration from him. It's sad that he's retiring but he has been, in my opinion, one of the best players."