THE political implications of a Scottish independence referendum bill are “irrelevant” when it comes to the Supreme Court’s decision-making, the Lord Advocate told justices as the indyref showdown kicked off in London.

Judges are seeking to establish whether the Scottish Parliament has the legislative competence to hold an independence referendum without Westminster’s permission.

During her arguments - made over the course of four and a half hours - to the court on Tuesday, Scotland’s most senior law officer Dorothy Bain KC argued that a referendum win for Yes would not directly guarantee independence, as this would be achieved through discussion between the UK and Scottish governments.

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However, she acknowledged that a vote would have significance just as the Brexit ballot had “great political significance”. She emphasised that it would be difficult for the UK Government to “ignore a decisive expression of public opinion” in the event of a Yes win.

Overall Lord Stephens, Lord Lloyd-Jones, Lord Reed, Lord Sales and Lady Rose were told that they were ruling on a point of law and should therefore not take into account the political impact. This, Bain said, is how the Supreme Court has handled previous references relating to the constitution.

She said: “Ultimately when it comes to determining the purpose of the provision (of legislation), and its legal effect, the political fallout of that is irrelevant for this court.”

Earlier, Bain told the court that it is of “exceptional importance” that the question of whether or not the Scottish Parliament can legislate for a second referendum on independence is resolved, adding that it is a “festering issue”.

The National: The Supreme Court hearing will take place over two days and conclude on WednesdayThe Supreme Court hearing will take place over two days and conclude on Wednesday

Bain KC also said the Scottish Parliament is not constrained when it is consulting the views of the Scottish people.

She explained there were various examples of the Scottish Parliament debating and passing motions on matters reserved to Westminster.

Bain said: “Scottish ministers, it can be argued, are not precluded from consulting the people of Scotland on a wide variety of issues.

“And they are not precluded to consult with the people of Scotland on the issue of independence.”

As Bain brought her oral legal arguments to a close, she said she was seeking the Supreme Court’s ruling on a “critically important question” and echoed comments made in her previously published written case.

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During the session, Sir James Eadie KC also began outlining the UK Government’s arguments to the court. His main points centered around the bill being in draft form and therefore not at the appropriate stage for it to be referred to the justices.

The UK Government’s representative argued that the Referendum Bill would have to be passed by the Scottish Parliament before a decision could be made on its legal competence.

He said such requirements were to ensure that a Bill referred to the Supreme Court was “as close to not being abstract… as possible” and reaches justices “in its final form” before potential royal assent.

He claimed the Lord Advocate was seeking “a judicial ruling in the abstract” and that justices giving opinions on “hypothetical” issues “draws courts into policy making”.

Eadie will continue his arguments between 10.30am and 3.20pm on Wednesday, with the Lord Advocate given 40 minutes to respond to them.

Once the court has adjourned, justices will take an estimated six to eight weeks to come to a conclusion, with Lord Reed noting that they had over 8000 pages of documents to get through.