It's worth saying that this isn't a done deal yet. The Bill still needs to pass the Lords. By all accounts the Lords is sounding hostile to the Bill and will try and put a whole pile of safeguards/blocks to the bill in.
What makes this particularly interesting is because it's a backbench vote which is free of the whip.
You need to understand the significance of this little issue.
It means the following. The Lords are in a position where if there is enough people who want to block the bill they may be able to do so for some time possibly indefinitely.
Protocols unofficially allow all manifesto pledges bills to ultimately be passed by the Lords.
Bills which are not manifesto pledges face ping pong between the Lords and the Commons, but ultimately the various parties will invoke the whip to help enable a bill to pass.
What makes this one unique is that it's a free vote. The parties will not be getting involved in this vote.
So there is no protocol to force it's passage and there's no political backing to force it's passage. It comes down to whether enough individuals in the Lords think the bill is robust enough and good enough to pass the Lords and into law.
Now there is a law which allows the Commons to force a bill through without the Lords support. This is the 1911 Parliamentary Act. This allows the Commons to pass something without the approval of the Lord's after it's got stuck for two parliamentary sessions (basically two years).
There's two problems with this:
There are ramifications for the Lords to do this - it might make them look undemocratic and encourage reform of the Lords and a weakening of their influence. But the Lords really could work on concerns about lack of safeguarding in the bill with the public to gain support for its position and to persuade more MPs to drop support for the Bill.
And the other problem is who needs to enforce the 1911 Parliamentary Act. Typically it's the government that holds the power to do this. But this is a private members bill and a free vote. Technically it could be done but there's no guarantees and it is more difficult.
Given how close votes already are, its probably going to be a while before this becomes law. And it could see a lot more amendments yet.