While the first rule of being a wedding guest is never to outshine the bride, that doesn’t mean dressing down for the occasion.

With an estimated two billion people worldwide watching last week’s royal wedding, the congregation temporarily transformed Westminster Abbey into a rainbow catwalk.

The Queen wore lemon yellow, mother-of-the-bride Carole Middleton opted for sky blue, while Prince Harry’s on-off girlfriend Chelsy Davy sported aqua green.

Style leaders Victoria Beckham, Tara Palmer-Tomkinson and Samantha Cameron chose very different ensembles involving headpiece, hat and hair jewellery respectively.

But their mantra was the same – let Kate Middleton have her ultimate fashion moment.

So, inspired by the glamorous guest list of royalty, celebrities and dignitaries, here’s a guide to how to dress to impress at those ‘I do’ occasions this summer.

Rules of Engagement

Royal nuptials aside, unless you’re attending a black tie or cocktail affair, the rules for a daytime wedding are slightly more relaxed – and you won’t have an audience of billions to scrutinise your choice of hat. Take note, Princess Beatrice.

“The goal is to create an outfit that’s cheerful and celebratory, ideally something similar to what you’d wear to a daytime religious occasion – but dressier,” explain Hillary Kerr and Katherine Power, authors of new book What To Wear, Where.

“But just because the ceremony and celebration take place in the sunshine (hopefully), don’t make the mistake of thinking you can turn up in any old thing.”

With photographic evidence aplenty on any average wedding day, your outfit shouldn’t become the talking point over the cutting of the cake.

“The trick to getting your daytime wedding look right is really paying attention to your choice of materials,” Hillary and Katherine advise.

“Avoid super-casual fabrics at all costs, meaning no jersey, cotton, or polyester. Instead, reach for lightweight dressy fabrics like chiffon or silk, as they will give you the right hint of formality.”

COLOUR MARRIAGE

Unless you’ve got the bride’s approval, stay away from white. Pale colours can also cause problems, risking accusations of stepping into the bride’s spotlight, according to Hillary and Katherine.

“You should never wear a white dress – this includes cream, ecru, and even nude. Avoiding white-heavy prints is imperative too. Our rule is the print cannot be 50 per cent white or more.”

Black might be the choice of colour for gothic nuptials and funerals, but keep things lighter for a summer wedding.

If you want a flattering dark shade, take Victoria Beckham’s lead and opt for navy as an alternative.

“Generally speaking, it’s better to stick to cheerful colours for daytime weddings: think light and bright,” say Hillary and Katherine.

“That said, you can wear black – especially if the wedding starts mid-afternoon and goes into the evening. Make sure your fabric is appropriate and add colour with accessories.”

AISLE WALK

Tread carefully with your choice of shoes for weddings. “Picking the appropriate footwear is of paramount importance, especially if the wedding is taking place outdoors on the grass or sand,” warn Hillary and Katherine.

“The best way to navigate nature is to go for a wedge. Stilettos, with their ground-puncturing skinny heels, are a perilous choice. Of course, if the day doesn’t call for such adventures, you’re free to wear a range of shoe styles.”

If you’ve got the height, don’t be afraid to shun the heels and ensure you’ll be the last one standing on the dance floor.

Hillary and Katherine say: “Nude pumps are always at the top of our list – they’re flattering and will make most party dresses feel more appropriate for daytime.

“An embellished flat sandal can work, too, especially if paired with an exotic-print maxi dress for a beach wedding.”