Alas I can’t find any news reports in the UK stating hundreds of thousands, that’s a really significant number of people for the UK, rather tens of thousands. Last year saw 300,000 pro Palestine protesters head to London, but it appears to be an over-‘estimation’ for this protest. Great to see people still going out in the UK though.
Vegetable stir-fry, curry or similar should be easily do-able. There’s plenty of fresh veg that will keep long enough out of a fridge or canned asian veg is decent. Tomato or pesto pasta. Stew made with canned beef isn’t bad. Omlette.
Do you have a cool bag/box? Grab a bag of ice and you have a fridge for a few days. Even a plastic box would do the trick.