While I don't have sources, I think it wasn't as simple as that. I've read that Alfred did have some chances to go outside, but he simply didn't take them.

All I'm saying is: from what I remember what I've read, it didn't seem to be the case that he was locked up. He kind of willingly let it happen. Whether that is actually true is another story as I can't remember the source where I read it from.

In any case, I do think there's more to this story than this submission is showing (after skimming through it).