In a globalised world, there is no cure for slavery | Simon Jenkins

Theresa May's modern slavery bill proposes tougher sentences for traffickers, but the line between voluntary migration and servitude is often vague

After a century of lecturing the outside world on the evils of slavery, Britain apparently needs to pass a law suppressing it within its own borders. There are an estimated 10,000 people living in slavery in Britain, a rise of "25% in a year", according to the home secretary, Theresa May – figures that look so vague they are hard to believe.

The tra...