Complete with Robocop style security and an inevitable huge police presence, Windsor Park was turned into something of a fortress last night. Still, Celtic were able to lay siege to Linfield, breaching their defensive lines again and again as they strolled through this first leg, second round UEFA Champions league qualifier.

When David Healy, the Linfield manager, admitted that there was “a lot to fear” from Celtic in his pre-match press conference, this might have been the kind of thing that he had in mind as Brendan Rodgers’ side showed their superiority in a game in which they barely broke sweat.

From start to finish this was little more than a routine late afternoon kick around for a Celtic side who had banked two goals before the opening period was at its halfway stage.

For the small pocket of Celtic supporters – contentiously arranged into the ground at the very last minute – it made for easy viewing. And while there were inevitable insults swapped, there was little real tension in the ground, until a flashpoint just after the hour mark in the second period.

Leigh Griffiths, starting ahead of Moussa Dembele, had caused havoc with his corners for much of the evening – he was the architect of both opening goals with his set-pieces – so much so that as he moved to take another one, he was rained upon with coins, cups and bottles from the Linfield supporters huddled at the corner flag.

Protesting to Spanish referee Alejandro Hernandez brought only brief respite, and as Griffiths moved to take the kick again, what appeared to be a Buckfast bottle flew past his head. Remonstrating with the whistler bizarrely brought about a yellow card for the striker, the most head-scratching conclusion to reach from the official and much to the striker’s irritation.

In any case, Rodgers hooked Griffiths after the incident and replaced him with Dembele, a decision that was made with the game effectively won.

It sparked an ugly period with Linfield chairman Roy McGivern getting out of his seat to address the supporters himself as he pleaded for calm after a small section continued throwing missiles onto the pitch and clashed with police.

Calm was restored and the focal fell again onto the pitch but it will not be the end of the matter for Linfield who will face sanctions from UEFA for the conduct of their support.

Griffiths was clearly still simmering at the full-time whistle but it was ill-advised to take a scarf from the Celtic support and tie it around the Linfield goalpost. Inevitably it provoked an immediate reaction with one Linfield supporter getting through security to run onto the pitch while riot police and dogs were then brought in to close around that particular pocket of the stadium.

It was a surly end for Griffiths who had been instrumental in establishing Celtic’s early lead in a game that they dominated without ever having to break sweat.

It was an inswinging corner from Griffiths which led to Scott Sinclair claiming the first competitive goal of the season for Celtic. The set piece fell to James Forrest, later replaced by Jonny Hayes, still inside the box and the winger scooped a looping cross onto the head of Sinclair.

It was a goal-wards header from close range that seemed to carry very little menace, but still it found its way over the line and gave Celtic their first significant toe-hold in the game.

It was an advantage that was quickly doubled when Tom Rogic, looking sharp and energetic throughout despite playing through the summer break, collected from another Griffiths cross and drilled the ball low into the net from the edge of the box.

From there on it, it was an exercise in damage limitation as Celtic controlled the tempo of the game.

Roy Carroll kept the scoreline down with a one-handed save from Sinclair, while an offside flag prevented another just after the restart from the interval.

In between times, Jozo Simunovic ought to have claimed a rare goal too after Mikael Lustig had collected from yet another Griffiths corner and his low, raking effort was narrowly missed being prodded in at the back post by the Croatian defender.

Craig Gordon had one save to make in the opening period but for the most Linfield were charged with trying to find a way to get the ball off Celtic.

Simunovic went into the book for a foul on Andy Waterworth as he tugged the player back, but it was Erik Sviatchenko, deputising for the injured Dedryck Boyata, who looked most likely to give Linfield their chance to take a goal to Glasgow.

At the other end, it was Carroll’s performance that kept the scoreline down as Celtic continued to calmly probe for openings.

There could have been more and doubtless at Celtic Park there will be more to come but last night’s work was done with the minimum of fuss.

With either Dundalk or Rosenborg awaiting in the next round there is every chance that the bar will be raised a little higher as Celtic look to get themselves back into the UEFA Champions League group stages.

It was the first step on a long road but there will be some satisfaction at the manner of the performance.