LONDON, Dec. 10  Some rock bands accelerate their tempos when they play their old songs decades after the fact. Playing fast is a kind of armor: a refutation of the plain fact of aging, all that unregainable enthusiasm and lost muscle mass, and a hard block against an old band’s lessened cultural importance.

But Led Zeppelin slowed its down a little. At the O2 arena here on Monday night, in its first full concert since 1980  without John Bonham, who died that year, but with Bonham’s son Jason as a natural substitute  the band found much of its old power in tempos that were more graceful than those on the old live recordings. The speed of the songs ran closer to those on the group’s old studio records, or slower yet. “Good Times Bad Times,” “Misty Mountain Hop,” and “Whole Lotta Love” were confident, easy cruises; “Dazed and Confused” was a glorious doom-crawl.

It all goes back to the blues, in which oozing gracefully is a virtue, and from which Led Zeppelin initially got half its ideas. Its singer, Robert Plant, doesn’t want you to forget that fact: he introduced “Trampled Underfoot” by explaining its connection to Robert Johnson’s “Terraplane Blues,” and mentioned Blind Willie Johnson as the inspiration for “Nobody’s Fault But Mine.” (Beyond that, the band spent 10 luxuriant minutes each in two other blues songs from its back catalog  “Since I Been Loving You” and “In My Time of Dying”).

Ahmet Ertegun, the dedicatee of the concert, would have been satisfied, sure as he was of the centrality of southern black music to American culture. Ertegun, who died last year, signed Led Zeppelin to Atlantic Records; the show was a one-off benefit for the Ahmet Ertegun Education Fund, which will offer music students scholarships to universities in the United States, England, and Turkey, his homeland.