New Bank Letter For Transfer Of Funds From Abroad - Needed?

[AyG]

I've extended my investment visa several times now. Each time I've gone to the bank first and got a letter stating that the funds came from overseas. Last year the immigration officer looked at the letter for 10 seconds, then gave it back to me. Previous years they've kept it. Since I've now moved, I don't want to have to drive hundreds of kilometres to get the letter if it's not really needed. Anyone got any experience of this?

Thanks.