Which is precisely why there won't be a second referendum.
Westminster won't grant a referendum it doesn't know it will win. In 2013, pro-indy support was typically in the 20s and low 30s - Cameron would have felt pretty secure approving a Section 30 order for the following year. As it turned out the way independence support balooned during the campaign, peaking in the mid-50s iirc, will have scared the sh!t out of Westminster. If they hadn't put aside party differences & teamed up for that final Project Fear onslaught, saving their fücking Union & annihilating Labour in Scotland in the process, we'd be independent now and laughing/crying as their calamitous Tory/Brexit sh!tshow slowly implodes. I should know - the bastards spooked me into being on the wrong side of history in 2014.
It's very, very different now. They wont - can't - repeat that stunt because they simply no longer have the ammunition. After 13 years of disastrous Tory 'government' there's no coherent argument that Scotland is better off on any level within the UK, and they cannot permit the independence movement the space to make the social, political and economic cases for independence that a legitimate, Westminster approved referendum campaign would allow. With the UK economy in the gutter, Westminster needs Scotland's wealth, natural resources and tax take more than ever, certainly moreso than 2014 and it's entirely absurd to think they'd ever gamble with losing it.
And if there was a referendum tomorrow - they would lose.