Explainer-Scotland's difficult route to another independence referendum

FILE PHOTO: Scotland's First Minister Nicola Sturgeon campaigns in Midsteeple Quarter for the Scottish Parliament election, in Dumfries, Scotland, Britain May 3, 2021. Jeff J Mitchell/Pool via REUTERS

LONDON (Reuters) - Scottish independence supporters are calling Thursday's election the most important in the nation's history as they vow that if they win a majority in the devolved parliament, they will push for another referendum on breaking from the United Kingdom.

The Scottish National Party (SNP) is close to controlling the devolved parliament - knows as Holyrood - outright in Thursday's election.