“Illustrious and unknown: this was what Degas aspired to be, and what Cy Twombly has become.” That’s how curator Kirk Varnedoe introduced Twombly to an ambivalent American audience at his retrospective at New York’s Museum of Modern Art in 1994. In the 14 years since, Twombly has produced one of the most astonishing, original, wrenchingly beautiful series of late work in art history. Tate Modern’s retrospective establishes a new status for Twombly based on this recent work, while demonstrating incontrovertibly its dependence on the artist’s lifetime of technical mastery and preparation.

This exhibition, curated by Sir Nicholas Serota playing at the top of his game, is a stunner not just for its splendour and clarity about an elusive artist but also as an exploration of art’s relationship with its past. No less than, though entirely differently from, his contemporary Andy Warhol – both born in America in 1928 – Twombly is revealed here as the postmodern artist par excellence, working in series as he pilfers and transforms sources old and new into his own lapidary, celebratory, death-haunted language. And whereas in 1994 it was uncertain whether he would be remembered as more than an illustrious postscript to abstract expressionism, in 2008 he stands as America’s greatest living artist and one who, in orchestrating a coda to that key movement, is creating something important for our own times.