you lot mucking about with fireworks

Hi, I heard this sentence from EastEnders and don’t really know what does it mean…

“I thought it was you lot mucking about with fireworks over there”

  1. What’s the meaning of “you lot”? are these two words come together as a subject?
  2. What’s the meaning of “mucking about with”? why there are two propositions coming after “mucking”?



‘You lot’ is similar to ‘You guys’ ‘You people’ but is a bit more derogatory. ‘Muck about with’ means ‘play about with’ ‘not playing seriously with’. It’s often used by an adult talking in a serious way to children who are misbehaving/making too much noise’ 'using something in a playful way , as for example an expensive piece of equipment: Stop mucking about with my computer. In its use you would use both prepositions with an object. If you were simply describing the way someone who is behaving in this away, you would simply say: Stop mucking about.