Super strict security check for transfer entire amount on my bank

I transferred all my amount in my bank to my friends account today because I left UK. Of course I needed not only a security number for the telephone banking, but also several information required maybe because it's a transfer of entire amount, not a part of. (I'm not supposed to describe the detail because it might affect a security of the bank). I talked 3 or 4 clerks and it took more than 30 min...