Who are Sinn Fein, why don’t their MPs take up their seats in Westminster and how could they affect the Tory government?

SINN Fein's stance of refusing to take their seats at Westminster made it all the easier for the Tories to join forces with Northern Ireland's DUP.

The IRA-linked party won in seven seats at the 2017 snap General Election — but what are their policies and how has their electoral success affected the government?

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