Depends on....
Whose name the flat is in. Who paid for the flat.
In the husband's name, paid by the husband, flat is
negotiable.
In the wife's name, paid by the wife, flat belong to the wife.
No argument there.
In the husband's name, paid by the wife, wife can get the money
back.
In the wife's name, paid by the husband, flat is a gift by
the husband to the wife.
It is a very good idea to get a very good lawyer.