Formal lunch at St James's Palace

[Bigbrassband]

I've been invited to a formal lunch at St James's Palace!
What to wear?

Please help me! I need some ideas, guidance, recommendations - budget as little as possible.

My vitals: 31, 5 foot 3, size 12, reasonable legs and norks. Long hair. Colours- soft summer, so blues, greens, off white, dusky pinks, aubergine.

I own this, it does have straps I can put on, perhaps with a light jacket or blazer?

I also have this

Do you think either of those would be suitable?

I think the second one is better, maybe with a blazer.

The first one is lovely but not formal enough, in this situation!

What colour will your companions be wearing?

Nosey, why are you attending?

I thought the same about the first one trainers, will save it for the evening pissup soiree!

I think my companion will be wearing a grey suit, probably with some kind of tie! I'm going with a friend who needs a plus one deepfried, quite exciting really for someone who never really does the formal thing

Now, now, Camilla. Everybody knows that you're not 31.

Duchy Originals keep one sprightly!

I think a knee, or slightly above the knee length, day dress - or a double crepe coat dress - with bracelet or elbow skirting sleeves - would be better. L K Bennett has a sale on. You see lots of the above there (a fitted day dress in cream, called "Tan" is on their site) if your budget would stretch, or there's Reiss or Zara. Pinks and creams are very on trend atm. You could wear this with one piece of good jewellery, heeled courts, or even sixties round toed heeled boots to give it a bit of an edge. (If you are really broke, charity shops can be great!!)
Having said this, I went there when heavily pregnant, and did not feel out of place in a blazer and comfy wide leg pants, cobbled together from the wardrobe and jazzed up with a pretty printed scarf! I think if you feel comfy it helps; there's lots of standing around.
I'm no royalist, but was impressed by way Charles made a huge effort - deliberately telling bad jokes, etc., to make people feel at ease.

What granita said on the clothes - any of those retailers would be ideal for purpose. Definitely not the first dress.

Thank you for the tips, they are hugely appreciated! I'm scouring the shops and Ebay with all your advice in mind.

Tried on the red dress and will wear it for the evening drinks with an unstructured grey blazer, grey heels, and a pearl bracelet.