Layout groups don't work

¡Hola! There everyone

I must be doing something wrong somewhere but my UI layout groups don't seem to function as I have seen elsewhere.

Basically I have set up my UI as described in various tutorials.

• Panel (with horizontal layout group attached)

  • Button

  • Button

  • Button

  • Button

With this I would expect the buttons to all expand equally to fill the entire panel, this is not the case. The buttons are staying really small and being really spaced out.

I can only assume I have missed something that has changed since the latest update to unity.

What I am aiming for is a panel that contains multiple buttons, these buttons should fill the panel in full with varying sizes depending on the size of the button text.