A FIRST-HALF brace from Orient's Sean Thornton was enough for the Londoners to take all three points in a tight and edgy game at the Matchroom Stadium.
Thornton's goals sandwiched Korey Smith's great strike for the league leaders, but with both Chris Martin and Anthony McNamee denied by the woodwork it was the O's who celebrated an important win which boosts their hopes of avoiding relegation.
After the game City boss Paul Lambert told First News: "No, we never got going. We never got on the front foot and we lost two really bad goals.
"That's the worst we've been for a while but we have to pick ourselves up and go again. We've still got a really good lead with four games to go, so we just need to dust ourselves down and get on with it again, starting on Saturday at Charlton."
Lambert was forced to make changes to his starting line-up, with Stephen Elliott and Oli Johnson coming in for the absent Grant Holt (suspended) and Wes Hoolahan (thigh).
City's huge travelling support were stunned when Orient took the lead after only three minutes. Scott McGleish's knock-down was chested down well by Sean Thornton before he rounded Fraser Forster and slid the ball in from an angle to put the home side in front.
But the Canaries didn't lose their heads and got themselves back on level terms thanks to a quality equaliser in the 19th minute. It came when Chris Martin played the ball in to the feet of Elliott and he laid it off superbly for Korey Smith to find the corner of the net with a well-placed 22-yard effort.
They nearly edged in front seven minutes later when Chris Martin picked up Drury's throw-in and tried his luck with a speculative effort from 30 yards which left O's 'keeper Jones stranded, but agonisingly bounced to safety off the foot of the far post.
Just when it seemed they were taking control of the game, Orient took the lead thanks to some slack defending from the visitors. As Daniels floated a free-kick into the box the City back line were caught in no-man's land and Sean Thornton slipped in behind them to head home the easiest of goals from close range - his second of the match.
Lambert didn't make any changes at the break as the Canaries looked to force their way back on to level terms. In the 54th minute Jimmy Smith was booked for pulling back Johnson as the City striker threatened to surge into the Orient box.
At the other end a neat move by the home side ended with Spicer's shot deflecting behind for a corner off the out-stretched leg of Michael Nelson.
Chris Martin was booked in the 63rd minute as he disputed a free-kick award with referee Graham Scott and within a couple of minutes Orient's Lichaj joined him in the ref's notebook for time-wasting when taking a throw-in.
Five minutes later Lambert made his first change of the evening in an effort to freshen up City's mis-firing attack, Anthony McNamee coming on for the hard-working Simon Lappin.
But Norwich were still failing to test Jones in the Orient goal and after Thornton was only denied a hat-trick by a finger-tip save from Forster, Lambert reacted by making a double substitution - Cody McDonald coming on for Elliott and Stephen Hughes replacing Johnson.
And Hughes nearly made an immediate impact, smashing Doherty's neat header into his path goalwards in the 81st minute, only for Jones to make a diving reaction save to beat the shot out.
With Norwich throwing men forward they were nearly caught on the break when Chambers burst through on the halfway line but his run was checked by Drury - a challenge which earned the City full-back a yellow card.
As the game entered injury time Anthony McNamee cut in from the left and then curled a delightful 22-yard effort which beat Jones all ends up but crashed against the far post and away to safety.
