Somewhere near the bottom of the invitation, usually in smaller type than the rest, there is a line about what to wear. Two or three words. No explanation. And those two or three words are doing a lot of work, because they are the only instruction you will get about a day you cannot dress for twice.
Here is what each of the common British codes actually means, what it means specifically for women, and what to do when the invitation says nothing at all.
Morning dress
This is the most formal daytime code, and it is more common in Britain than almost anywhere else. If the ceremony starts before four in the afternoon, particularly in a church, and particularly if the groom's side is in tails, you are likely to see it.
For women it means a day dress or a smart dress-and-jacket, and it is the one code where a hat or fascinator is genuinely expected rather than optional. Hemlines sit at or below the knee. Nothing strapless, and nothing that reads as evening: heavy satin and deep jewel tones look out of place at eleven in the morning.
A printed or softly coloured maxi works here too, as long as the fabric is light and the neckline is covered. Something like Clemence sits in the right register, though you would want a jacket or wrap over the shoulders for the ceremony itself.
Black tie
The most formal evening code. Ceremonies under black tie usually start late afternoon and run into the night.
For women that means a floor-length gown, or a cocktail-length dress in a fabric that clearly belongs to the evening: silk, satin, velvet, lace. The fabric matters more than the length. A full-length dress in a light everyday cloth will look less correct than a knee-length one in proper satin.
No hat. Evening codes drop headwear entirely, which catches out people who have only ever been to daytime weddings.
Our Evening collection is cut for this end of the scale.
Black tie optional
The most common code at British weddings now, and the least helpful phrase on the list, because it means the couple would like you dressed up but will not insist.
Read it as: black tie, minus the obligation. A long dress, a tea-length dress, or an elevated cocktail dress all work. In practice the room will split roughly evenly between floor-length and knee-length, and nobody will look wrong. What does look wrong is treating the word "optional" as permission to dress down — it is an invitation to be less formal than black tie, not to arrive in something you would wear to lunch.
Cocktail
Dressy, but not gowned. The hemline lands anywhere between the knee and just above the ankle, and again the fabric does the work: silk, satin, crepe, lace rather than jersey or cotton.
This is the code where a satin midi earns its place. Odette was cut for exactly this: pleated satin, keyhole neck, finishing below the knee.
Lounge suit
A British phrase that confuses people because it describes what the men wear and leaves women to work it out. It means an ordinary business suit for men, which places the day one notch below black tie.
For women: a dress, smart separates, or a trouser suit. Midi length is the safe centre. You are aiming to look like you made an effort for a formal occasion without competing with the evening codes.
Semi-formal, smart casual, and other vague instructions
These two are the least reliable words on any invitation, because they mean completely different things depending on where the wedding is. Semi-formal at a country house hotel is not semi-formal at a pub garden.
The venue tells you more than the code does. Church and hotel lean formal. Barn, garden, or pub leans relaxed. A midi or maxi dress, a jumpsuit, or a skirt and top will all sit comfortably in this band; the decision to make is how dressy the fabric should be, and the venue answers that.
Garden party and outdoor weddings
Less a code than a warning about the ground you will be standing on. Stilettos and lawns do not get along, and no amount of planning fixes a heel that has sunk three inches into wet grass. Block heels, wedges or flats.
Bring a wrap. British afternoons that start warm rarely end that way, and a dress that was perfect at two o'clock can be unwearable by eight without a layer. This is also the band where a printed maxi does its best work — the Wedding Guest edit leans this way.
Beach and destination weddings
Lightweight fabrics, flat or wedge shoes, and a hemline you can walk in on sand. Chiffon and lighter prints are the natural fit. Anything structured or heavy will be uncomfortable within an hour.
When there is no dress code at all
This is the most common situation of all, and the one nobody writes guides about.
Work backwards from three things: the time the ceremony starts, the venue, and the season. An afternoon ceremony at a registry office followed by dinner at a restaurant is a cocktail-adjacent day, whatever the invitation does or does not say. A two o'clock church wedding with a marquee reception is a daytime formal wedding. A Saturday evening at a hotel is closer to black tie optional than to anything else.
If you are still unsure, ask someone in the wedding party. It is not a faux pas — it is a normal question, and every couple would rather answer it than have a guest spend a fortnight guessing.
The two colour rules
White, cream and ivory are still out, unless the couple has explicitly asked for them. This has not loosened, and "but it has a pattern on it" is not the exemption people hope it is. If the overall impression from across a room is white, choose something else.
Black, on the other hand, is no longer the problem it once was. At a formal or evening wedding, black is entirely acceptable and often the most elegant option in the room. At a garden wedding in July it will simply look heavy — that is an aesthetic judgement, not an etiquette one.
One more, less discussed: if the couple has named a palette for the wedding party, avoid it. Matching the bridesmaids is nobody's idea of a good photograph.
The short version
Match the formality of the fabric to the time of day, match the shoes to the ground, and when in doubt, ask. Everything else on this list is detail.