Leyton Orient 1-2 Man City: Pep Guardiola's side survive a scare to progress to FA Cup fifth-round after the hosts took an unlikely lead at Brisbane Road

The goal they will talk about for many years in his corner of East London and which will take its place in the rich history of Leyton Orient is not the winner scored by Kevin de Bruyne. It was not even scored by an Orient player. It is the own goal by Stefan Ortega in the first half after a wonderful 50-yard effort by Jamie Donley had crashed into bar, hit the Manchester City goalkeeper as he back-pedalled into panic and settled into the net.

That was the goal to light up another FA Cup weekend and send them dancing in celebration on the balconies of the flats overlooking Brisbane Road, which these days goes by the name of the Gaughan Group Stadium. It also inspired Richie Wellens and his League One team to believe they could be on course to create one of the great upsets and heap a little more misery upon Pep Guardiola and his Premier League champions.

Orient led at half time and were level until the 79th minute, by which time Guardiola had been forced to summon De Bruyne and Phil Foden from the bench and had something like a first team out on the pitch. Premier League power won the day but Wellens and his team were incredible. Still fighting for an equaliser at the end when captain Dan Happe volleyed wide at the back post. Orient have been in excellent form ever since goalkeeper Josh Keeley scored a late equaliser in the second round of the Cup against Oldham. That was another remarkable goal, one to spark a season into life, propelling them towards the play-offs in League One.

City though arrived in East London and casually rolled out a trio of new signings, freshly acquired at a cost of £140m as if to remind everyone of the vast financial gulf between these two clubs. There were debuts for Gonzalez, a 23-year-old midfielder from Porto who slotted into the Rodri role until he was forced off with injury midway through the first half, and teenage Brazilian centre-half Vitor who must not have envisaged many days like this when he signed from Palmeiras.

Erling Haaland took the day off and Omar Marmoush led the line, flanked by Savinho and Jack Grealish, who registered City’s first effort of the game, cutting in from the left wing and slamming a low shot into the advertising boards. Ilkay Gundgoan scuffed wide an even better chance to dampen Orient’s early spirit. The League One side had already proved they were capable of disturbing Guardiola’s young defence. Kelman tore about making life uncomfortable for them. The centre forward on loan from QPR forced a save from Stefan Ortega, when he burst clear of Reis on a slick break out of defence.

And he won the ball for the opening goal, dispossessing Gonzalez on halfway. Donley pounced as it ran loose from the challenge, fired it towards goal with his left boot from the best part of 50 yards out and the whole of Leyton seemed to hold its collective breath as it found its way into the net via the woodwork and the goalkeeper’s backside. City claimed a foul on Gonzalez, who was soon forced off and replaced by Bernardo Silva but none was given. And, with no VAR in the FA Cup until the next round, the home crowd were free to launch into celebration.

Wellens came down from his seats in the stands where he started the game to reorganise to defend the lead as City assumed control of the ball and dominated for long spells. Orient massed around their own penalty area, crowded out their passing channels and hurled bodies heroically in the line of shots. They also did their best to disrupt any rhythm and Guardiola could be seen grumbling in the ear of the fourth official as the home side did what they could to eat into the clock.

Keeley made an exceptional save at the end of the first half to deny Marmoush from close range. The Egyptian seemed certain to score as he slid onto a cross from the right. It looked like any contact was enough and he made contact and yet Keeley somehow kept it out. Still, Orient to their credit carried a real threat when they broke into the open space created by City’s territorial dominance. Sonny Perkins flashed on shot over after a crisp counterattack and Ortega made a strong save to keep out a deflected effort by Donley after City failed to clear a corner.

Guardiola’s half-time response was to change both his centre halves. Off went Reis and Ruben Dias, and on came Abdukodir Khusanov and John Stones. Khusanov, a fortnight after his debut to forget against Chelsea, quickly made a vital contribution cutting out a cross from Perkins bound for Kelman at the back post. Then another, this time blessed with fortune when he deflected a shot by Rico Lewis into the net while trying to get out of the way.

It brought relief for the visitors but did little to change the pattern of the game. Orient sat deep and picked their moments with care. Kelman went close from a free-kick whipped towards the near post by Donley and forced another save from Ortega. In between, City probed for an opening with patience wearing thinner. James McAtee, hat-trick hero in an eight-goal romp against Salford in the third round, was not far wide form the edge of the penalty box and Keeley saved from Gundogan.