Flowers can be a budget-busting expense.

London florist Philippa Craddock has been tasked with decorating the chapel for the ceremony.

Her team plans to use white garden roses and peonies, and many of the plants will be sourced from royally owned gardens, according to Kensington Palace.

The local sourcing may help keep costs down.

Even so, Simon predicts floral work for an event of this scale would cost at least "£50,000, and that's being conservative."

Craddock did not respond to a request for comment.