LONDON: Jenson Button is to partner Fernando Alonso at McLaren next season. The team are to announce their driver line-up at a news conference at their factory in Surrey on Thursday.
But BBC Sport has learned they have decided to retain Button after weeks of leaning towards Kevin Magnussen.
Button, the 34-year-old 2009 world champion, will continue into a 16th season and has his wish granted to test himself against the man widely regarded as the best in F1.
McLaren signed Alonso some weeks ago, but had been vacillating over the identity of his team-mate.
McLaren's 2015 partnership
Fernando Alonso Jenson Button
33 Age 34
Spanish Nationality British
2 World titles 1
236/32 Races/Wins 268/15
97 Podium finishes 50
Chairman Ron Dennis had been keen to retain Magnussen, 22, but the continuing delays over making a decision have tipped the balance back in favour of Button.
The two were evenly matched for pure pace in 2014, with Button out-qualifying the novice 10-9 in 19 races.
The Englishman scored more than twice as many points as Dane Magnussen over the season.
McLaren had intended to retain Magnussen, who finished second on his F1 debut in this year's season-opening Australian Grand Prix, on the basis that the team's data had suggested he was fractionally quicker and had youth and promise on his side.
But Button's strong finish to the season, his experience and perhaps unrest at boardroom level over Dennis's position has influenced the team to go the other way.