May I answer? I think if you ask for bonds it means that only people who have the cash up front will be able to come and visit again.
Of course, you can do a number of things to make the system harder for people to get in, but my question is, at what cost, and who are you excluding? I would certainly hope that we don't end up with a system that makes it so hard that only the super-rich and the super-connected people and those who have all the connections with MPs and high-paid lawyers will be able to come here.