Outdoor eventer trial - What to wear?

[Finnbob]

I've decided to be brave and entered our first outdoor eventer trial this sunday but don't know what to wear! It just says 'suitable clothes' on the schedule. Non peak hats, back protectors and medical cards compulsory so do I assume its full xc attire or do I go for showjumping jacket and shirt?

help please!

 

[kirstyfk]

I would take both just in case but i would think it means you can wear your xc stuff.