What should I wear to a DofE Buckingham Palace afternoon event?

[Pandersmum]

Does anyone know how formal the dress code is for DofE Buckingham Palace afternoon event?

Will I need a jacket?

Any dress suggestions? size 18/20, large chest 5’8 tall.
Budget upto £100. Must have sleeves.

thanks in advance

Assuming it's this, the dress code is "smart". The video of the 2024 event should give an idea? Need for jacket will depend on weather.
https://www.dofe.org/do/gold-award-celebration/london/

Thanks! I’ve had so little info from DC, I hadn’t thought about checking the website!