“Why so serious?” say the teaser posters for the forthcoming Batman movie, The Dark Knight. This slogan acquired a bleak subtext last night when 28-year-old Heath Ledger – who plays the Joker in the new film – was found dead in his New York apartment, apparently as the result of a drug overdose (the autopsy is to be held today). As anyone who has seen Monster’s Ball or Brokeback Mountain can attest, Ledger was a hugely talented actor whose troubled private life seems to have overwhelmed him. But, in one of the darkly ironic tricks that Hollywood plays, his death will ensure that his performance as the Joker is watched with completely different eyes as an artistic suicide note, the psychotic display of a disintegrating man who is only pretending to be pretending. The truth, as ever, is probably much more pedestrian: Ledger’s demise may turn out to have had more to do with Thoreau’s “quiet desperation” than with grand gesture. But – accidentally, miserably – he has just bought a place in cinema legend.