Why do double-breasted jackets and coats often have a buttonhole at the top of each lapel whilst single-breasted jackets and coats only have a buttonhole at the top of the left lapel? It is because double-breasted jackets and coats symmetrically have both buttons and buttonholes down the left and right sides whilst a single-breasted jacket or coat only has buttons down the right side and buttonholes down the left side. The buttonholes at the top of the lapels reflect what’s below. Though peaked lapels on a double-breasted jacket never fold over and close like single-breasted notch lapels sometimes do on sports coats, pea coats and some double-breasted overcoats—like the greatcoat—are able to fasten up to the top. These coats do have a button on each side either under the collar or at the top of the chest for the lapels to fold over and fasten to. The two buttonholes on a double-breasted coat are carried over from these more functional garments.
Dimi Major put a buttonhole in each lapel of George Lazenby’s double-breasted car coat and blazer in On Her Majesty’s Secret Service. Douglas Hayward made Roger Moore’s double-breasted blazer in For Your Eyes Only, his double-breasted suit jacket in Octopussy and his double-breasted dinner jacket in A View to a Kill with a buttonhole in each lapel. Brioni put a buttonhole in each lapel in Pierce Brosnan’s double-breasted blazer in GoldenEye and in his double-breasted overcoats in Tomorrow Never Dies, The World Is Not Enough and Die Another Day. Sean Connery’s, Roger Moore’s and Pierce Brosnan’s naval uniform jackets and Roger Moore’s naval greatcoat all have a buttonhole on each lapel, and the greatcoat’s lapels can close to the top. Daniel Craig’s greatcoat in Quantum of Solace also has a buttonhole in each lapel, and like Roger Moore’s greatcoat it can close to the top.
Cyril Castle, however, only put a single buttonhole in the left lapel in Roger Moore’s double-breasted chesterfield and silk suit jacket in Live and Let Die and Roger Moore’s double-breasted suits, blazer and white dinner jacket in The Man with the Golden Gun. A single lapel buttonhole on a suit jacket discards the ancestry and symmetry of having two lapel buttonholes for instead considering only the actual usage of a suit jacket’s lapel buttonhole: the boutonnière. Even when there is a buttonhole in both lapels, only the left buttonhole should be used for a boutonnière if you are so inclined to wear a boutonnière.
Daniel Craig’s Billy Reid pea coat in Skyfall also only has a lapel buttonhole on the left, which takes into account the reality that even if the lapels were closed, only the left side would actually fasten over to a button on the right. There wouldn’t be a jigger button at the top of the coat like there is at the waist. Since the Billy Reid pea coat has peaked lapels and no buttons at the top, it actually can’t close at the top like a traditional pea coat could anyway.
Angelo Vitucci didn’t put any lapel buttonholes in the two double-breasted dinner jackets in The Spy Who Loved Me and Moonraker and the double-breasted blazer in Moonraker. This is the coward’s solution for those who can’t decide if a double-breasted jacket should have a lapel buttonhole in the left lapel or both lapels. Though history and symmetry says there should be a buttonhole in each lapel of a double-breasted jacket, it’s not a faux pas to have one buttonhole only in the left lapel. No lapel buttonholes at all ends up looking cheap and leaves no place to wear a flower.