supporting documents

I was looking through AN form and it is asking for one of the following supporting documents for evidence of freedom from immigration time restrictions. It does not list BRP as an option. This is silly but do I need to find home office letter that came with BRP? shouldn't the brp be sufficient?

SECTION 5 Evidence of freedom from immigration time restrictions:required for all applicants except those covered by SECTION 4 above.
•Your passport showing permission to remain permanently in the UK Or
•The Home Office letter by which you were given permission to remain permanently in the UK
•If you came to the UK as an asylum seeker you should have evidence of appeal applications Or
•Evidence of being freely landed

It means ILR approval letter, since BRP is subject to loss/renewal. But I also think letter accompanying ILR BRP also states to keep the letter safe. So personally I think either of the two letters should suffice. I would also suggest to click here and book NCS as well. Good luck.