Hi all. Hope someone can help understand my problem and how I can fix it.

I had a trip to Severn bridge yesterday to get some photos done late at night with long exposure. On the way back I realised the headlights were crazy dim. I check any other electricals on, and turned them off and they still stayed dim. However, fog lights (high beams) and blinking lights were as strong as usual. Even driving at high speeds 60mph didn't change the strength of the main lights.

Do anyone have any good ideas on what the problem is? Or what I can check. Trying to avoid going to garages and potential expensive fixes here.