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. The only time the SNP have won a majority before in 2011, Britain's then-Prime Minister David Cameron bowed to pressure and agreed to a referendum in 2014. Scots then voted by 55-45% to remain in the more than 300-year-old union.