Trent Alexander-Arnold feels an appropriate person to discuss what Jurgen Klopp calls “the second most important game you can play” and not merely because, at the tender age of 23, he is already midway through his third. Liverpool’s history in European Cup or Champions League semi-finals dates back to 1965 and incorporates eight times when they have progressed to what Klopp terms the biggest match of all, but Alexander-Arnold was the architect of their greatest moment on this stage. It was his quickly taken corner, when only two people in Anfield felt alert to the possibility, that led to Divock Origi’s decider against Barcelona three years ago.