RETOUCHING: GLOSS STUDIO. PHOTOGRAPHY ASSISTANTS: SIMON ROBERTS, HUAN NGUYEN, AND MARU TEPPEI. STYLING ASSISTANT: JEAN HALL.

IRVINE WELSH IN NEW YORK, MARCH 2014. T-SHIRT: CALVIN KLEIN UNDERWEAR. RINGS: WELSH'S OWN.

JAMES MCAVOY IN FILTH. PHOTO: COURTESY OF MAGNOLIA PICTURES.

EWAN MCGREGOR ON THE SET OF TRAINSPOTTING, 1996. PHOTO: POLYGRAM FILMED ENTERTAINMENT /PHOTOFEST.

JONNY LEE MILLER AND KELLY MACDONALD IN TRAINSPOTTING, 1996. PHOTOS: MIRAMAX /COURTESY OF EVERETT COLLECTION.

DANNY BOYLE, EWAN MCGREGOR, AND IRVINE WELSH ON THE SET OF TRAINSPOTTING, 1996.

ROBERT CARLYLE AND JONNY LEE MILLER IN TRAINSPOTTING, 1996. J