What should I wear to an MBE ceremony at Windsor?

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I’m off to Windsor with someone who is receiving their MBE in early October. What shall I wear?

Is a hat required? Happy to splash out a bit so long as I can rewear the outfit at some point.

I went in May to accompany someone for the same thing. There’s a dress code when they send the invite (I think). Yes wear a hat or fascinator, the prefer block colours (although I wore a jewelled gown). People were all dressed as they wished tbh. Smart - but could be dress or trouser suit, jumpsuit, national dress etc.

I wore a fascinator and dress. To be honest anything goes - I saw trousers, dresses, separates etc. I think the invitation said ladies should wear hats or fascinators. Wear comfortable shoes as you may be standing for a while. My friend was in the last batch of recipients and I was standing for over 2 hours.