Suella Braverman appears to have missed major flaw in her Rwanda policy, says Nigel Nelson

As the small boats Bill sailed through the Commons last week, polygamy was not an issue.

Perhaps it will be when the proposed legislation gets its predicted mauling in the Lords and the Home Secretary might find she has to deal with this one further down the line should a migrant arrive on a dinghy with several wives in tow. Polygamy has been illegal in Rwanda since 1962.

But as things stand the only rule for setting up a harem in the UK is that the weddings must take place in one of an A - Z of 58 countries from Algeria to Zambia where polygamous marriages are allowed.

This might be an example of Ms Braverman’s controversial statement that some of those who wish to come here from other cultures do not share British values.

Brits are inclined to value one spouse over many, though it is surely a tribute to British broad-mindedness that our nation’s laws respect the marital arrangements existing elsewhere in the world.

In Islam the rule first introduced by the Prophet Muhammad that men could take up to four wives was a way to create an early welfare system. It meant that women who lost husbands in battle could be looked after by being decently remarried and their new husbands were under an obligation to treat each equally.

As the religious historian Karen Armstrong says, the Qur’an gave “women a legal status that most Western women would not enjoy until the nineteenth century”.

What no one seems to know - not Number 10, the Home Office, the Department for Work and Pensions nor even the Office for National Statistics - is just how many polygamous unions there are in the UK. Or polyandrous ones come to that as women can take extra husbands in parts of India, Nepal, China and Kenya.

And when polygamy does pop up it plays havoc with both the benefits system and immigration rules. The 1988 Immigration Act got round this by forbidding a UK resident from sponsoring a spouse visa if they were already married to someone else, though wives 2, 3, and 4 could still come to Britain if they could find a way to qualify in their own right.

The old benefits system allowed all wives to claim means-tested handouts, but only the first got the full amount. When Universal Credit came along it did not recognise polygamous partnerships so only husband and earliest wife could make a joint claim, and extra spouses were treated as single people. This turned out to be good news as, according to a report in February by the House of Commons Library, that way they get more money.

Granted, polygamy is not one of the most pressing issues in Ms Braverman’s attempts to stop boats crossing the Channel. But it is another example of what she’s not thinking about while rushing through life-changing legislation.

Along with the more immediate concerns expressed by Theresa May and Iain Duncan Smith over the way she is driving a coach-and-horses through modern slavery protection, there is also Tim Loughton’s worries about detaining unaccompanied children, or the, as yet unspecified, safe and legal routes for genuine refugees to get here.

Nearly every change in the law causes unintended consequences.

What is most alarming about pushing this one through Parliament so prematurely is that not even the intended ones have been worked out yet.