Trent Alexander-Arnold’s quick thinking led to Liverpool completing one of the finest comebacks in Champions League history on Tuesday evening.Jurgen Klopp’s tactics and Georginio Wijnaldum’s brace helped as well, of course, but it was the 20-year-old's wits that led to Liverpool scoring the fourth goal that secured a dramatic 4-3 win.The Reds won a corner in the 79th minute when Alexander-Arnold noticed that Barcelona weren’t ready to defend it.He quickly whipped the ball into Divock Origi, who smashed the ball past Marc-Andre ter Stegen to make it 4-0 on the night.Everyone was caught off guard. Indeed, Luis Suarez appealed against the goal being allowed.

But the fact of the matter is that Barcelona were caught off guard, and they’re no longer in the Champions League as a result.

Special praise should also go to the ball boy who quickly gave a football to the Liverpool right-back.

Liverpool helped by ball boy's rapid reactions

It was the young lad’s hurried actions that made Origi’s goal possible.

And yet it was a moment that came with plenty of planning.

The Independent have revealed how Liverpool’s match analysts realised during the first leg at Camp Nou that Barcelona’s players moaned and became distracted whenever they conceded a free-kick or a throw-in.

They would protest even if the decision was blatantly correct.

And so Klopp sent a message through the club, with his message reaching Carl Lancaster, a coaching mentor at the club’s Kirkby academy.

Among Lancaster’s responsibilities is the co-ordination of ball boys and he instructed the lads to return the football as quickly as possible in the second leg.

This was picked up on by 14-year-old Oakley Cannonier, who wasted no time in serving Alexander-Arnold with 11 minutes to go.

And now, Cannonier is an Anfield hero.

The youngster sometimes trains with two age groups above his natural level. There are now calls for Liverpool to send him to the final in Madrid.

What a lovely tale.