Help, I don't understand

I've got a job contract in front of me. I don't understand: You are entitled to a total of 31 days' annual paid holiday (which will be deemed to include holiday and holiday pay in lieu of public and bank holidays).

Does that simply mean the public and bank holidays are included in those 31 days? If so, why does it say "in lieu of"? Doesn't that mean "instead of"?
Earlier it says I could be asked to work on public and bank holidays. So does it mean that I would be paid a holiday pay, even if I work? So it would be just like an ordinary day's work for me?
Or does it mean that if public/bank holidays occur on days of the week when I don't work, I will be paid extra? But, in that case, I would be paid anyway...
Or does it mean something completely different?

Sorry, I don't get it! Thanks

That clause does not list what days you get offetc.

But it does tell you that you get 31 days in total off that would normally be work days.

That includes days you take off plus the holidays that fall on business days.

Like the fourth of July today!!

But if you are unclear on a provision, ask them to explain.