Verdi called his first attempt at Simon Boccanegra a “wobbly table”, which he fixed with major revisions nearly a quarter of a century later in 1881. The phrase hung in the mind at the start of Covent Garden’s staging of this later version, directed by Ian Judge and conducted by John Eliot Gardiner.

Several 11th-hour cast changes, together with John Gunter’s oppressive, post-modernist fixed set didn’t bode well. First seen in 1997, its topsy-turvy mix of medieval Genoa and Risorgimento Italy lets in no daylight, with little sense of the all-embracing sea so audible in Verdi’s score.

At first the ponderous action failed to match the music’s glinting ebb and flow, played with precision and intensity by the ROH orchestra under Gardiner’s impassioned direction. Then, post-interval, everyone suddenly pulled together with sharper focus and energy. If the set looked no better, the performance crackled into blazing life, reminding us why this overlooked opera, almost Shakespearean in emotional complexity, can be counted one of Verdi’s finest. The chance to hear it, whether in this or the original 1857 version, always rewards.

As Amelia, German soprano Anja Harteros made her house debut with stylish conviction and vivid tonal range. Marcus Haddock’s Adorno had lyrical dignity at his terrible moment of remorse. Marco Vratogna (Paolo) mustered snakish venom. Ferrucio Furlanetto, a luxury last-minute cover for illness, excelled as Fiesco.

In the title role, Lucio Gallo struggled at first, dragging the pace and flattening top notes, but proceeded to deliver a performance of heartfelt integrity and psychological depth.

Verdi’s great study of leadership shows how a flawed man with a buccaneering past learns wisdom, forgetting old enmities for the good of the city-state he loves.

In his first week in office, London’s new mayor should get over to see it — fast.

Until 24 May (020 7304 4000)