One of Scotland's leading historians, Sir Tom Devine, has warned the SNP it only has another five years of political dominance in which to secure its aim of independence.

Speaking at the Edinburgh International Book Festival, the historian said that the First Minister, Nicola Sturgeon, had not yet been properly tested but suggested she would be in the years to come.

Sir Tom, who supported the Yes vote at the 2014 independence referendum, told a packed audience: "I am still in favour, as the final option, in the independence option, but if you consider the situation at the moment, it is extremely dangerous.

"Unlike the press, worldwide, not simply in Scotia, I don't think yet that [First Minister] Nicola Sturgeon has been tested.

"The big tests are still ahead, and they are awesome, and particularly the timing, if there is going to be one, of any new referendum for independence.

"At the moment the auguries are moving pretty bad, I would say they are worse than could argue that the recent Brexit decision could be a symbolic trigger for another vote, but in one sense it adds to the European instability, and of course we now know in terms of what went on in the voting in 2014, that many people were concerned with risk, and instability produces risk.

"At the same time, there has been no intellectual response to the weaknesses of the SNP economic programmes, not simply in relation to the currency, but elsewhere."

He added: "It is an awesome situation to be in because my own feeling is that I reckon they have at most, the current government that is, before depreciation of their support, probably at most another five years to go, maybe six or seven at the outside, and during that period if they are not going to avoid a Quebec situation, then they will have to make a decision one way or the other."

Sir Tom was discussing at the event his book Independence or Union with the event's chair, Allan Little.

The historian said that the "mesh" of Scottishness and Britishness that bound Scotland in the Union was not easily broken and had proven to be "tough old gut."

He said the SNP could succeed if "serious and rigorous" work is done on their arguments and there is clear evidence that there is "clear evidence" in the deterioration in the UK following the Brexit vote.

The historian also added that he didn't think 'the departure from Europe" would happen.

"Is that controversial enough for you?" he added.