The Tottenham defender with the chronic knee problem had not played for his country for three years, but his comeback, alongside Rio Ferdinand in central defence, was encouraging on two fronts.
First he scored the opening goal in last night's 3-1 win over Mexico with a header from a corner. Then he completed the full 90 minutes on Wembley's heavy pitch to prove his fitness.
For someone whose international career seemed to be at an end when he was called up for the matches against Slovakia and Ukraine 15 months ago but released without so much as completing a training session, just pulling on the England shirt for the 20th time was a major achievement.
King said: "It's been a long time coming. I didn't know whether I would play again for England and it makes it all worthwhile. I wouldn't say it was one of my best games but it was tough because Mexico are a good side."
However, King has much more to aim for. England manager Fabio Capello will now rest him for Sunday's final warm-up match against Japan in Graz. But it seems certain King will be part of the 23-man squad Capello unveils on 1 June, and the 29-year-old is certain his body can cope with the demands of a five-week tournament.
He said: "With the knee I'm confident. This season I've had problems with the muscle but I've put that behind me now and got games under my belt. I played three games in the last week of the season so it proves I can do it and can play games in quick succession. And the Wembley pitch was quite energy sapping.
"The more I play the fitter I get, and the medical staff are doing a brilliant job to help me prepare for the games. I will try to be as fit as I can and we'll see where it goes."
Although he took time to adjust to his new surroundings, King did improve as the match went on after scoring his first England goal for six years. "Is that all?" he quipped when reminded of the statistic. "That was a nice touch but the main thing was the team getting a result. We played against a good side and found it difficult at times but we got the result."
While King lasted the entire match, Ferdinand played just the first half, with Liverpool's Jamie Carragher taking over at half-time, also ending a three-year exile from England colours, the difference being the Liverpool man's was self-imposed.
Ferdinand, however, was certain King had done enough to convince Capello his body can stand up to the rigours of a four-week tournament. Ferdinand said: "Ledley's a good player and good players play well alongside other good players. I enjoyed it. We both enjoyed it. He got a goal as well, which was great.
"From set-pieces everyone knows we are fairly decent and in the tournament hopefully that bodes well for us. Ledley had a great chance to show the manager what he can do and I thought he did a great job.
"Mexico qualified for the World Cup and they are a good team. We knew we were in for a tough game but by the end of it we were the team that controlled it."
As a relative newcomer to the squad, King is in a good position to assess the impact of the present regime compared to what has gone before. And he has no doubt who has made the biggest difference to the England side since he was last in it.
"There's a lot of different personnel," said King. "But what we do have is a manager who is a proven winner. At every level he has managed at he has achieved."