Hayter has really written a book against the British New Labour Government and Campsfield Immigration Detention Centre.
In terms of a case against "immigration controls" (which is a term that is not defined anywhere in the book) you have to wait until chapter 5.
And when you reach chapter 5 (which is 23 pages or so) there is nothing intellectually revealing or even punchy to really get people's attention. Hayter opens up chapter 5 with, "The strongest case against immigration controls is that they impose increasingly harsh suffering on migrants, including refugees". Spoken as if no one knew this! She then links this with undermining human rights like the right not to be tortured or the right to work in the UN Declaration on Human Rights, but it seems to me that referring to the prohibition on torture in the European Convention on Human Rights is not very relevant when torture has a high test in the strasbourg courts and there are so many qualifications to the rights relied on. Fundamentally, I wondered why Hayter hadn't defined "immigration controls" or categorised them or distinguished between them, so it's an open question if the book does what it says on the tin.
The argument made in her book that immigration controls are racist might appear, to readers not at first familiar with famous examples in the field of eugenics, bold and daring when it's not well explained what conception of "control" she is concerned about and, for example, whether any of the examples in her book are a control about immigration numbers or a control concerned with internal economic resources within countries or a control concerning citizenship and the reader might ponder about this. Hayter's economic arguments for free movement of people appear more interesting but what about other social and political and other rights? There is no normative argument for this.
The book seems a little, if not increasingly, outdated with its references to newspaper articles and stories and anecdotes. Bursting with energy, it needs an update and a torch shining light.