The votes will be counted on 23 September

Eligibility for voting is a little more complicated, because the party does not operate a one member one vote system.

The system is open to a combination of constituency and branch representatives, MPs, MSPs and MEPs, affiliated organisations like the student wing, elected members of the national council and other office bearers.

In total, around 800 delegates will have a say this September on who leads the party into the general election.

Other facets of the system include:

• Delegates only have one vote each

• Every constituency association has four delegates.

• Each branch within a constituency is entitled to two delegates for its first 50 members - or part thereof. For each additional block of 50 (or part of 50) members they get another delegate - put simply the more members, the more votes a branch has.

• Sub-branches of 10-25 members have one delegate each.

• Four affiliated organisations can each send six delegates - Federation of Student Nationalists, Young Scots for Independence, Association of Nationalist Councillors and trade union groups.

• MSPs, MPs, MEPs have one vote each.

• 30 elected members of the national council each have one vote.

• 24 members of the national executive committee - the party leader, deputy leader, vice conveners and office bearers - also have a single vote each.