Anyone know what kind of tool is needed for this?

[mashandsausage]

Pic isn't good quality sorry but it's a circle with a small hexagon (I think) shape in the middle? I'm not good at this and I live alone so no idea what tool would be needed to undo this?? Thanks in advance!!

An Allen key. You can pick up cheap sets of them in pound shops.

Yes. Allen key. They normally come in bunches of different sizes and look like little metal capital Ls.

It's hard to be certain from the photo but it looks like a hex nut. You want something like a Draper 33869 Metric T-Handle Hexagon 10 Keys Set.

Google it. There's some on Amazon and Screwfix and B&Q are bound to have them as well

I just googled Allen keys haha yeah that's defo looks like what is needed! Thanks so much everyone