Why you should NEVER wear bright colors, silk dresses or feather hats to a wedding, by celebrity wedding planner JOHNNY ROXBURGH who reveals the secrets to a perfect guest outfit

The invitations line the mantelpiece, the presents are bought, the hotels are booked. Now all you have to do is decide what to wear to this summer’s crop of weddings.

Who better to advise you on the many fashion pitfalls to avoid than society wedding planner Johnny Roxburgh, who has organized weddings for the rich and famous and personally attended hundreds of them.

Here he explains which colors to avoid, the best size for your hat and handbag – and a trick that will make any dress flattering.

How big is your bag?

I recommend you don’t bring an oversized handbag that looks like you’re about to do your weekly shop in Peter Jones.

You don’t want a giant tote bag stuck between your legs all day. I get by with just a pocket in my pants.

What you want is a bag that is discreet and beautiful; a bag that can sit on the table while eating, as part of the decor, or hang over your chair and look stylish.

Linen is out, chiffon is in

Be very careful with linen. You really need to think about how you’re going to get to the wedding and how long you’ll be in a car. Too long and your backside will look like you just crawled out of bed. It’s no coincidence that you never see the royal family wearing a fabric that crushes.

If you bought something particularly light, such as chiffon, that doesn’t wrinkle, take it to a good tailor and have it weighted down. They can sew small weights into the hem of the skirt to help it hang flatteringly – and reduce the risk of the skirt riding up in the wind and exposing your panties.

You also need to consider the social impact of your sleeves. Draped sleeves look elegant, but are a nightmare when it comes to the wedding breakfast or if the dishes are meant to be shared. You’re dragging all the excess into your food (and everyone else’s). Don’t let fashion overtake practicality.

The perfect hat height

Do not wear a hat that may block other guests’ view of the bride during the ceremony. I would also avoid a huge plume of feathers. It’s not ideal to kiss a fellow guest and have an ostrich feather stuck up your nose.

Choose a style that is no wider than 18 inches and no higher than eight inches. Ideally, it should also be one that can be worn at an angle so that others can easily approach you for a kiss.

If you wear a top hat, you may have to accept that you will be sitting at the back of the ceremony or no one else will be able to see it.

You can’t wear a tiara if you’re a guest at an afternoon wedding…unless you’re true royalty or it’s white tie and evening.

Opt for a jeweled headband or something smaller with a birdcage veil; something that you won’t wear every day, but that won’t overpower the rest of your look or irritate fellow guests.

Heels vs. flats

Guests should always check the wedding venue online before risking ruining a pair of £1,200 Louboutins on a long gravel driveway. Above all, shoes should fit properly; no gaping leather on the sides.

Cheap shoes will always yawn when you walk in them. Expensive shoes that fit well, not.

Go as high as you want with the heels, but you have to be able to walk in them. And if the reception is on a lawn and you’re standing on stilettos, of course you’ll sink. I prefer to see beautifully decorated flats that still look special and show that you did your best.

Your color code

It’s best to avoid strong colors like fuchsia pink or bright turquoise at a wedding, otherwise you’ll be unmissable in every photo and no one will thank you for it. It’s a very fine line between looking glamorous and smart and trying to steal the show.

It’s the bride’s day and you should never try to mislead her. It remains the ultimate deadly sin. For the same reason: go easy on the sparkle. You want a subtle decoration on the cuffs or neckline.

Sequins from head to toe look like you’re looking through the photographer’s lens and can be noisy when you walk. Heads should turn for the bride, not for you zipping down the aisle.

Choose a palette that suits your environment. If the reception is being held in beautiful grounds and gardens, try flowers, but avoid anything overwhelming. Subtle and elegant is always preferable to attracting attention.

Ban beachwear

No rompers or playsuits, and certainly no shorts, no matter how fitted they are. Save them for the beach.

And if you are someone who gets very hot, my advice is to avoid silk. Any moisture on it will tend to spread and it will be very difficult to hide.

Instead, opt for a well-cut jumpsuit. Choose one in a special fabric: brocade or jewel-toned velvet, no pinstripes. Or palazzo pants are a chic alternative that will not look out of place in a ballroom, on the balcony of a country house or in a stately garden while enjoying champagne.