THE pain of that wretched home defeat to CFR Cluj and the failure to reach the Champions League group stages for the second year running is sure to linger for some time to come for Celtic.

Yet, reaching the Europa League is by no means, especially in the circumstances the Glasgow club were forced to play the second leg of their play-off in last night, an achievement to be taken lightly.

This fine 4-1 win over AIK in Sweden and emphatic 6-1 aggregate victory will ensure the Scottish champions are in the draw in Monaco alongside glamorous names like of Arsenal, Manchester United, Porto, Roma and Sevilla in Monaco this afternoon.

An early strike from James Forrest, an own goal from Oscar Linner in the first-half, a late Christopher Jullien effort and an injury time Lewis Morgan header secured their objective and also repaired much of the damage done by the Cluj reverse.

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The conduct of Celtic supporters, alas, once again left much to be desired. Several flares were set off as the game got underway and stewards wearing hard hats and carrying buckets of sand had to go in to the stands to put one of them out. Smoke filled the multi-million ground for some time afterwards. Ugly skirmishes then broke out between local police and a small number of away fans at half-time. Punches were thrown and batons were used.

It was a dark night for Celtic and the tarnished reputation of Scottish football and another UEFA punishment is certain to follow.

Still, it was impossible to extinguish the spirits of the jubilant players who had secured European football until at least Christmas on the park at the end of a hugely satisfying 90 minutes. They went a some way to atoning for the crushing disappointment they suffered earlier this month with this accomplishment.

Celtic will go into their first meeting of the 2019/20 campaign with Rangers at Ibrox on Sunday with their confidence high even if Kristoffer Ajer and Odsonne Edouard fail to recover from knocks.

Neil Lennon’s men were favourites to progress before kick-off having won the first encounter with Rikard Norling’s charges 2-0 last Thursday night. But being without right back Hatem Elhamed and centre half Jozo Simunovic complicated their task considerably.

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The visiting manager was forced to play Nir Bitton, whose preferred position is in midfield, alongside Jullien, a summer signing who has taken some time to settle, in the heart of his rearguard. With Boli Bolingoli, another close season acquisition whose defensive displays have been erratic to say the least, outside them at left back it was far from ideal.

When Ajer, who had been deployed at right back, limped off injured in the 15th minute with the scoreline still at 0-0 it was the very last thing that Celtic needed. He was replaced by Anthony Ralston, a youngster with limited experience.

AIK had started impressively. Kolbeinn Sigthorsson, their Icelandic striker, struck the right post with a volley in just the second minute. The Friends Arena may have been far from full, but the 30,000-strong crowd still made it an intimidating atmosphere for the visitors.

Forrest, though, silenced them a minute after Ajer had gone off when he put Celtic ahead. He made a powerful run into the AIK box from deep, received the ball from Edouard on the right wing, controlled it with his right foot and then rifled a left foot shot beyond AIK keeper Linner.

That left the hosts needing to score four times to prevail. They continued to attack in numbers and were rewarded for their efforts with a penalty when Montenegrin referee Nikola Dabanovic ruled that Bolingoli had brought down Sebastian Larsson inside his own area in the 33rd minute. The defender protested his innocence and it did look like a harsh decision by the match official.

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Larsson stepped up and sent Craig Gordon the wrong way. The AIK midfielder buried his spot kick into the bottom right corner as the Celtic keeper dived to the left. The equaliser sent the Black Army in the North Stack wild.

But their joy was short-lived. Celtic took the lead just a minute later when Johnston outsprinted Larsson to the goal line, cut the ball back and Linner turned it into his own net with his outstretched left arm under pressure from Ryan Christie. Once again, AIK needed four goals.

It was certainly a lucky break, but the lead by no means flattered the triple treble winners. They created as much in the final third as their rivals. Christie forced Linner to tip over his crossbar just before the end of the first-half with a long-range attempt. Forrest also went close from a tight angle early in the second.

At the back, too, they withstood the pressure they were under and kept their cool with passions ran high and robust challenges were flying in. Gordon, who has much to prove following the arrival of Fraser Forster on a season-long loan deal last week, did superbly to deny Nabil Obasi in the 47th minute. Ralston, another whose future prospects are in doubt, can be proud of how he acquitted himself.

Lennon made his first substitution in the 70th minute when he put on Lewis Morgan for Mikey Johnston. Six minutes later Vakoun Bayo took over from Edouard up front. Jullien scored from a few yards out with four minutes or regulation time remaining and Morgan netted in injury time to round off a professional performance.