Cigarette lighter (phone charger!) not working

Hi,

My cars cigarette lighter/power socket has stopped working - it seemed to work fine but when I used an adaptor that allowed two USBs and charged two phones at once it stopped working so I assumed the fuse had blown.

I had a look at the fuses and the diagram that was there - I’ve looked over and over again and from what I can tell, there is no fuse in the spot for this power socket. I thought it wouldn’t even run without a fuse so how it worked in the first place I dont know? Is the fix as simple as put a fuse in?

Thanks!