The milliner is creating accessories for a number of people attending the nuptials and says the strict dress code has limited the choices for those who will attend the marriage service in London's Westminster Abbey on Friday (29.04.11).
She said: "I'm making hats for quite a few of the guests. The invitation says 'hats must be worn in church', and forbids decorations; flowers or feathers, so most of the pieces I am making are bigger hats. People are nervous about what they can and can't wear, and other milliners I have spoken to have said they are making mostly larger hats as well."
"I think there will be more big hats and that people are moving away from the one feather look. I think there will be lots of upturned brims, so people can be seen; there's lots of kissing to be done!"
Jess - who was originally hired to design a hat for Kate's mother Carole Middleton - admitted guests are wary of looking foolish and are opting for "subtle" hues in their headwear.
She added to vogue.co.uk: "Most people have said they want subtle elegance: it's a Royal Wedding and the line between elegant and garish is fine. Everyone has said they don't want to feel like a fool. The hat has to complement the outfit, but people aren't going matchy-matchy. It's more about subtle tonnes of a colour."