The 125 candles on Celtic's birthday cake were outblazed by a result that flared around Europe as they administered Barcelona's first defeat of the season courtesy of a Victor Wanyama header and a dazzling strike on the break by the 18-year-old Tony Watt, despite a frantic late rally that saw Lionel Messi score his inevitable goal.
Yet fate had dealt Lennon a mixed hand over the course of the day. On the one hand he was relieved by the news that Georgios Samaras had overcome the ankle injury which caused him to be replaced during the first half in Barcelona. However, that positive development was countered by the absence of Scott Brown — understood to have succumbed to a virus — which added the Celtic captain to a casualty list that deprived the manager of Emilio Izaguirre, James Forrest and Gary Hooper and left him thin on the bench, which included three teenagers — Watt, Dylan McGeouch and John Herron.
The alternatives available to Tito Vilanova were immense by contrast — Gerard Pique, Cesc Fabregas, David Villa, to name but three. In such circumstances, when Celtic's sinews required to be stiffened and spirits to be summoned there could not have been a more inspiring backdrop than the teams encountered when they took the field to a stunning array of spectator-borne colours which spelt out a tribute to the club's 125th anniversary, superlative even by the standard of such choreographed displays.
It would be preposterous to suggest that a player of the stature of Lionel Messi would have his composure troubled by such a demonstration of fervour, but the Argentine was seen not to be wholly superhuman, first when he gave away possession casually and then when he banged a shot over in unrefined fashion.
Messi was to display a moment of characteristically wondrous skill before the half was out — when he accepted a prompt from Andres Iniesta and juggled the ball from right foot to left and off the crossbar in less time than it takes you to read this description of the attempt. So swift was Messi's reaction that it required examination of the slow motion TV replays to discern that Fraser Forster had actually got the tips of his glove to the shot, a detail which also eluded the match officials.
By that time, though, the most explosive development had seen Celtic seize the initiative. Just as they had done in the first meeting of these sides they took the lead from a set piece and, in another common factor, Charlie Mulgrew provided the service. Midway through the half Celtic, propelled forward by Wanyama's forceful running from midfield, won a corner kick on the right.
Aware that Barca were short of height in the centre of defence, Celtic had put in their work on the training ground. Mulgrew's delivery was pitched perfectly beyond the back post into precisely the unguarded spot that was filled by Wanyama as he timed his run perfectly to beat the unwary Alex Song to the punch and head sweetly past Victor Valdes.
The priority for Celtic was to preserve their lead to the distant interval, a feat that had eluded them in Catalonia, where Iniesta equalised just before the break. If possession is oxygen, Celtic were sucking scarce breaths as Barcelona refused to yield the ball and there were two heart stopping moments. One came when Danny Alves crossed for Alexis Sanchez to cushion a header beautifully across Forster but, just as it looked as though it was bound to cross the line, the ball skipped off the far post and out.
The other was an Alba cutback bound for Messi's straining boot until Forster inserted a hand to divert and allow Kelvin Wilson to clear. Barca became increasingly frantic followed the break but a world class Forster stop thwarted Messi and it was the goalkeeper who got the assist, with a kick from hand, when Watt left Mascherano for dead to finish perfectly and ensure a victory which could not be diverted even by Messi's strike in stoppage time as the skies over the east end of Glasgow boomed to the Hoops' euphoric anthems.