Blue striped shirt by Marks and Spencer, in their Blue Harbour Luxury collection.  100% cotton.  Long sleeves.  Button-down collar.  Chest pocket.  Contrasting trim in turquoise and white stripes.  Button cuffs.

Actual garment measurements:

Chest 46 inches (maximum).

Shoulder to shoulder 19 inches.

Length at the back 30 inches.

Sleeve length, shoulder to end of cuff, 26 inches.

Sleeve length, armpit to end of cuff, 21.5 inches.