Sinn Fein has called for a vote on Irish unification after Brexit.
The issue was raised this week when the prime minister held talks with Northern Ireland’s parties in Belfast.
Downing Street believes the majority of people continue to support the current political settlement – and the PM has pledged to protect the “precious union”.
We have heard warnings about the impact of Brexit on the UK before.
Former prime ministers Sir John Major and Tony Blair warned about it before the 2016 EU referendum.
As she tried to drum up support for her original Brexit deal last month, Theresa May warned a no-deal Brexit could strengthen the hand of those wanting Irish unification and Scottish independence.
With some increasingly concerned about the prospect of the UK leaving the EU without a deal on 29 March, concerns about Northern Ireland’s future appear to be increasing.
‘Dangers are real’
“A no-deal Brexit is the way that’s most likely to lead to a border poll and to people questioning the benefits of being in the United Kingdom,” one cabinet minister told the BBC.
“The dial hasn’t been moved – the dial could be moved in those circumstances.”
“The dangers are real,” adds a separate senior cabinet minister.
This source believes there is a danger that people without a strong nationalist or unionist background could react badly to a no-deal Brexit – especially if it leads to serious issues at the Irish border – and that could tip the balance.
‘Do your homework’
Not everyone agrees.
Another minister said the government had “a lot of get-out-of-jail cards” that could help it avoid a border poll.
When I put some of the concerns raised in cabinet to this person, they accused others of being “remarkably unwilling to do their homework on the issue”.
But the source added: “If there really is a horror show… the polling might reflect it”.
It’s worth pointing out Brexit would not be the only factor if there is to be a border poll; changing demographics would play a significant role too.