Russell Slade's first return to Withdean Stadium since his sacking as Brighton boss was a sweet one as his Leyton Orient side eased into the second round of the Johnstone's Paint Trophy with a 2-0 win.
Goals in each half from ex-Seagulls winger Dean Cox and Ryan Jarvis wrecked below-par Brighton, whose fortunes were summed up by Glenn Murray's 50th-minute penalty miss.
Cox gave Orient the lead against the run of play in the 21st minute with a deflected shot over goalkeeper Casper Ankergren after Stephen Dawson pulled the ball back to him.
Cox came close to adding a second four minutes later when he sent a volley against the crossbar, and later crossed accurately for Jarvis to head wastefully wide.
Orient keeper Jamie Jones denied Brighton before the break by twice thwarting efforts from striker Ashley Barnes before tipping over Liam Bridcutt's goalbound shot.
Jarvis doubled Orient's lead two minutes after the break, heading in a free-kick from Matthew Spring from 12 yards. A foul by debutant Orient defender Aaron Brown on Murray gave the Brighton striker the opportunity to reduce the arrears from the penalty spot, but his side-footed effort was saved by keeper Jones diving to his left.