Soup for 100!

[pollysproggle]

What is your favourite soup recipe please?

I do a charity Christmas lunch every year for the elderly, roughly 100 people. I always go with a soup starter as it's easiest and I'm looking for inspiration.
We don't have a massive budget and I'll need about 30 litres of the stuff so not too complicated a recipe. Also has to be vegetarian so it suits everyone.

Many thanks!

Lentil. A little goes a long way and it is cheap. Onions, carrot and garlic sweated in some butter. Add lentils and stock and Bob is your inlaw

Lentil
Leek and potato.

Both easy, cheap and popular.

Carrot and coriander or curried parsnip could work, simple and tasty. Easy to make in advance and reheated or can be kept warm in soup kettles.

Definitely lentil, it can sit for ages and just be topped up with water/stock if it gets a bit thick. Can add loads of different veggies to make it exciting for not much outlay.

I just like veg broth usually broth mix carrot turnip leek and either potato or parsnip. I buy diced root veg for quickness

Ooo lentil sounds good, I don't want anything that needs blending too much as it's such a large quantity so that could be perfect.
We did leek and potato last year.

Spiced parsnip sounds good too, if you were having parsnips in the main lunch would that be too much parsnip to have a soup too?