Transplanting the pyrotechnics across the Atlantic, London Has Fallen imagines a coordinated terrorist attack in retaliation for a G8-sanctioned drone strike in the Punjab province that slaughters dozens of innocent bystanders.
"Vengeance must always be profound and absolute," declares the film's archvillain, justifying the next 90 minutes of wanton collateral damage and workmanlike digital effects that reduce England's seat of political power to smouldering rubble.
A serious philosophical debate about the ethics of war is low on the list of priorities for four screenwriters who use expletives as punctuation and toss clunky one-liners into the fray as punchlines to the deaths of bad guys.
Die Hard and countless imitators have traversed this blood-smeared territory before and Najafi's picture offers nothing new to an overcrowded genre.
Chases and bone-crunching fight sequences nod respectfully to the Jason Bourne saga, including a centrepiece shooting match on the disused Jubilee Line platform at Charing Cross that minds the gap between realism and testosterone-fuelled fantasy.
Two years after a fateful drone strike that was supposed to kill terrorist mastermind Aamir Barkawi (Alon Aboutboul), the British Prime Minister dies suddenly in his sleep.
Statesmen and women from around the globe gather at short notice for the funeral.
Among the attendees are US President Benjamin Asher (Aaron Eckhart), German Chancellor Agnes Bruckner (Nancy Baldwin), Canadian Prime Minister Robert Bowman (Nigel Whitmey), French Prime Minister Jacques Mainard (Philip Delancy) and Italian Prime Minister Antoni Gusto (Alex Giannini).
Aided by his son Kamran (Waleed Zuaiter), vengeance-seeking Barkawi dispatches a gun-toting militia to infiltrate the heavily guarded ceremony with the intention of assassinating the world leaders who sanctioned the drone strike.
Secret Service Agent Mike Banning (Gerard Butler) takes charge of protecting the President and his boss, US Secret Service Director Lynne Jacobs (Angela Bassett), aided by defiant Metropolitan Police Chief Hazard (Colin Salmon) and plucky MI6 agent Jacqueline Marshall (Charlotte Riley).
Meanwhile back in Washington, US Vice President Allan Trumbull (Morgan Freeman) is horrified to learn that Barkawi is behind the atrocity.
"This man is responsible for more deaths than the plague," growls Trumbull.
London Has Fallen delivers all of the high-decibel thrills and spills that fans will demand, but little more.
Certainly characterization and plot are paper thin, and Butler and Eckhart both possess miraculous powers of healing, emerging from successive hails of bullets without a scratch.
Moments of unintentional hilarity, like the name of the new British Prime Minister or one American TV reporter's dramatic assertion that a couple of explosions have "decimated most of the major landmarks in the British capital" keep the tedium at bay.