The INSIDER Summary:

When wearing a suit, always leave the bottom button open for the waistcoat and jacket.

The tradition dates back to king Edward VII from the early 1900s.

He unbuttoned the bottom of his waistcoat because he was too fat.

He unbuttoned the bottom of his jacket to pay homage to the riding jacket that suits replaced.



There's a basic rule when it comes to buttoning up a suit jacket: "Sometimes, Always, Never" — if you have a three-buttoned jacket, sometimes button the top one, always button the middle one, and never button the bottom one.

In a two-buttoned suit, you should always button the top button and never the second.

Regardless, no matter what kind of suit you're wearing, the bottom button should never be buttoned up.

For a waistcoat, there's a similar rule: always leave the bottom button open.

It's fashion gospel for men (women are generally allowed to button the bottom button). Men's suit designers often even tailor the fabric so suit jackets and waistcoats looks more flattering unbuttoned at the bottom.

But it's also a strange fashion rule — why have a button if you're not going to use it? Where does this tradition come from?

The answer goes back to a very fat king: King Edward VII.

The story of King Edward VII (who ruled from 1901 to 1910) is often dismissed as a myth — but it's completely true.

As fashion blogs and magazines will tell you, there's a story that King Edward VII, back when he was the Prince of Wales and suits were becoming in vogue, got too fat for his waistcoat so he stopped buttoning the bottom button to make it fit better.

Out of respect for him, the British court — and, eventually, everyone else in England and the British colonies — stopped buttoning their bottom buttons, too.

Edward VII, on the right, with Prince George, on the left, in 1901. The bottom of Edward's waistcoat is undone. Wikimedia Commons

The "Edwardian theory," as it's called by GQ UK's fashion director Robert Johnson, isn't always taken seriously. It sounds too silly to be true. But historians of British fashion consider it fact, if a little muddled over the years.

The truth is, Edward VII set the trend for unbuttoning the bottom button on waistcoats as well as the bottom button on suit jackets, but for two very different reasons.

Suit jackets are unbuttoned at the bottom because they replaced horse-riding jackets.

The story of the "Edwardian theory" is told by Sir Hardy Amies, an English fashion designer who was the official dressmaker for Queen Elizabeth II for nearly four decades — between her ascension to the throne in 1952 to his retirement in 1989.

His fashion house is on Savile Row, a London spot famous for its bespoke tailored men's suits, so Sir Amies knows a thing or two about suits and courtly fashions.

The Duke of Roxburghe at Buckingham Palace in 1910, after the death of King Edward VII. The bottom of his suit is unbuttoned. W. G. Phillips/Phillips/Getty Images

In a 1992 lecture he gave to The Royal Society for the Encouragement of Arts, Manufactures and Commerce, he traced the story of "The Englishman's Suit" from 1670 to his present day. The single-breasted suit of today was first introduced in 1906, and was referred to as "a lounge suit."

It had three buttons, but it was still a little different from the suit of today — it was meant for more casual wear, and had a loose cut so that it looked best when the wearer was holding the reins of a horse. As Amies noted, "of great importance" was to "control the drape the position of the button at the waistline."

The "lounge suit," therefore, began to replace traditional riding coats. The third buttons of riding coats sat below the waist, so they had to be unbuttoned so the jacket draped properly while someone was sitting on a horse.

Edward VII decided that the top button should also be undone because it "looked common," according to Amies, leaving only the middle button to secure the coat.

Leo knows what he's doing. Jerod Harris/Getty Images for National Geographic Channel

When the lounge suit jacket started to become common as an everyday fashion, Edward VII kept the bottom button undone to pay homage to the riding coat style they replaced.

Waistcoats are unbuttoned at the bottom because Edward was fat.

Edward VII had a "legendary" appetite, according to the Oxford Dictionary of National Biography.

"He ate a full meal at breakfast, luncheon, tea, dinner (normally twelve courses), and supper," the dictionary reads. "He drank moderately, but usually smoked twelve enormous cigars and twenty cigarettes a day."

Sir Hardy Amies, Queen Elizabeth II's dresser, on his 90th birthday in 1999. He wore a suit perfectly. Dylan Martinez/Reuters

Edward was also legendary for his attention to men's fashion. In a discussion following Amies's lecture, a fellow of the society asked Amies about waistcoats, and why the bottom buttons of waistcoats (like jackets) should be left undone. Amies said that tradition is also attributed to Edward.

"Edward VII always left his bottom waistcoat button open because he was fat," Amies answered. "He found it more comfortable and everybody copied it. Waistcoats are now cut for the last button not to be done up."

The trend, the Oxford Dictionary notes, "was followed in this in Britain and the empire but not on the continent or in the USA." But nowadays, unbuttoning the bottom of the waistcoat is the norm.

Suit jackets generally have two buttons nowadays.

Three-button jackets are pretty common, but in the last 40 years, suits have trended toward having two-button jackets. You'll see only two buttons on some of the most trendy suits, like the J.Crew Ludlow. In that case, follow Edward's advice in leaving the bottom button unbuttoned, but do button the top one.

For Amies, though, the ideal suit was in the 1980s, when three buttons were still in vogue.

"The more I look at the three button suit — fastened at the waist correctly, the upper button left undone with an insouciant air, the lower button unfastened, paying homage to the riding coat curves — the more pleasing I find it to the eye," he remarked. "Its proportions are right."