I have a very old filing cabinet that I bought today from a shop that is closing down. It is locked and has no key. It is a full size, tall cabinet by Milners Safe Company LTD.
I'm not sure if it even has a lock, as the hole in the front of it seems a bit big for a key. But still, the drawers won't open.

Underneath, there is a bar coming out of the bottom at the back, which I think may be the locking mechanism, but I am really only guessing, as I have no idea.
Does anyone have any ideas?

Many thanks in advance.
Sarah