Whether or not the latter of those things can make up for the absence of the former is the big question on La La Land’s mind, and the answer isn’t as glib as you might expect. Behind the film’s nimble comedy and exuberant musical set-pieces beats a complex, crisply written romance, the power of which creeps up on you slowly then strikes in the film’s second half, in which Sebastian and Mia’s ambitions and relationship become increasingly tricky to reconcile.