Arsenal edged to a nervy 1-0 win against FC Zurich to secure their passage through to the Europa League knockout stages as group winners on Thursday night.
It wasn't as simple as desired, but it was job done nonetheless.
After Tierney gave the Gunners a first-half lead with an excellent strike from distance, they had to endure some tense moments after they failed to find a second goal.
With PSV winning at Bodo/Glimt, a Zurich equaliser would have seen Mikel Arteta's side slip to second in the group and left them facing a round of 32 play-off with one of the teams dropping down into the Europa League from the Champions League.
And there was certainly lots of worry in the air as the hosts struggled to build on their ascendency during a scrappy second half.
Zurich even had the ball in the net with 20 minutes remaining, but Adrian Guerrero's close range effort was correctly ruled out for offside.
Arsenal did hold on for the win, however, which saw them top the group and avoid extra fixtures later this campaign.