The Democratic Unionist Party (DUP) made gains in Northern Ireland in the general election, winning 10 seats, and may play a pivotal role in the future of British politics.
After the election ended in a hung parliament, Conservative leader Theresa May did not resign. But said that she would form a government with support from the DUP, her only realistic option as the the Liberal Democrats strongly disagree with her "hard Brexit" stance and ruled out any deals.
After it became clear that the Conservatives had lost their Commons majority, Foster told BBC Radio Ulster that it would be "difficult" for May to survive.
But a DUP MP later told Sky News that the party would "consider a supply and confidence arrangement to make sure Theresa May has sufficient support to keep her in government". He added that the support would "cost the Conservatives a lot".
After seeking permission from the Queen to form a new government, May announced that the Conservative Party would rule in an informal coalition with the DUP.
A socially conservative party, the DUP is strongly in favour of leaving the European Union but wants a soft Brexit, which it will demand in return for its support in propping up the Conservatives.
Concern has been raised in the past about the party's hard-line stance against gay marriage and extending abortion rights. Foster has vowed to prevent the Abortion Act 1967 from becoming law in Northern Ireland, even in the case of rape or fatal foetal abnormality. She has also blocked legislation supporting gay marriage.
"No-one wants to see a 'hard' Brexit, what we want to see is a workable plan to leave the European Union, and that's what the national vote was about – therefore we need to get on with that," DUP leader Arlene Foster has said previously.
On Brexit, the DUP want the border with the Republic of Ireland to be as "seamless and frictionless" as possible. They reject Sinn Fein's call for Northern Ireland to be granted a Special EU Status as they think this waters down their Britishness.
The DUP manifesto included retaining the triple lock on pensions, cutting VAT for tourism companies, and reviewing ferry prices between Northern Ireland and Great Britain.
Labour Shadow-Chancellor John McDonnell labelled an alliance between the DUP and Conservatives a "coalition of chaos. I can't see a stable government coming from that," he said.