The brand's chief creative officer enlisted the 22-year-old star to sing at the catwalk show after being impressed with him, and admits he got emotional watching him sing in rehearsals ahead of the main event.
He said: ''There were technicians, lighting people, photographers preparing, cleaners cleaning ... it was a chaotic thing.
''But then Tom started to play and the whole place went completely silent. And I stood there, trying not to show that I was getting a bit emotional - but it was just one of those moments: Tom completely went into lockdown, into what he was doing.
''He completely made sense, and I was just blown away.''
Despite experiencing worrying moments at the company, Christopher insists all his troubles felt eradicated when Tom belted out that first note.
He added to The Guardian newspaper: ''Whether you're fitting the collections or whatever kind of thing you're doing, where everything becomes so unimportant because that feeling, that idea is so powerful.
''You might have tonnes of worries about other things and life is chaotic. But all of a sudden you don't care about anything else.
''That example of Tom playing in rehearsal was one of them. Nothing else mattered.
''And those memories you have to cherish.''