How do I delete the FIRST partition from a 2 partition disk?

So I've finally managed to get Big Sur installed!

I now have 2 partitions (Containers?) on my disk;

One for Catalina and one for Big Sur.

I'd like to delete the first one and resize the second one to take up the entire drive. In disk utility I cannot delete the first partition for some reason.

Anyone know if this is possible?

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https://preview.redd.it/k2q3vcxdp5q61.png?width=2168&format=png&auto=webp&s=f7f0f65481ce08650007c9e2ab65a694ed60274f