Please help Notary public question

Hello all,

I am a British citizen and sponsoring my brother from Pakistan to visit the UK. I sent him all the necessary documents including a visa invitation letter to the high commission of Pakistan which I signed and dated, but his agent is telling him that this letter must be signed by notary public or your visa will be rejected.
My question is does it HAS to be signed from them?

Please share your experience.

Thx

Nonsense. The agent is talking crap.

Thank you, that's 1 No. waiting for the rest.