With the announcement last week of the appointment of violinist Laura Samuel to the post of leader of the BBC Scottish Symphony Orchestra, the long-running saga of orchestral leaders in Scotland moves one step closer to conclusion.

Regular readers will recall a situation in Scotland when all three national orchestras – the Royal Scottish National Orchestra, the Scottish Chamber Orchestra and the BBC Scottish Symphony Orchestra – had one thing in common: not one had a leader.

The leader of the RSNO for many decades, Edwin Paling, had gone off to the Antipodes to start a new life. The leader of the BBC SSO, Elizabeth Layton, had left the SSO for a different part of the world in controversial circumstances that were never explained by the BBC, although I understand a settlement was reached. And the young leader of the Scottish Chamber Orchestra, Christopher George, fell victim to focal dystonia and gave up playing.

All this raised provocative questions: what is an orchestra leader for? What do they actually do? There is no single answer; every orchestral musician and every conductor would have a different reply.

But aside from the big questions, the big picture in Scotland is now this: with the appointment to the RSNO of dual permanent leaders James Clark and Maya Iwabuchi, each of them absolutely outstanding in different ways, the RSNO ensemble has a new and audible sense of focus and purpose. The SCO is a different kettle of fish. The 37-strong orchestra is one of the world's supreme chamber orchestras, whether led by assistant leader and first violinist Ruth Crouch or distinguished guest leaders including former leader Alexander Janiczeck and, occasionally, the Scottish Ensemble's artistic director Jonathan Morton. The SCO will neither hurry nor be hurried in the recruitment of a new permanent leader. "The process is ongoing" they said this week.

The BBC SSO is different again. Since the departure of Layton, the front seat of the orchestra has been occupied by many distinguished and experienced guest leaders. But, in conversation on the subject, chief conductor Donald Runnicles has been quite explicit about the need for a new and top-flight permanent leader. "Next to the appointment of a chief conductor, it is the single most important appointment for an orchestra to make," he said at our last interview.

He went further. As chief conductor he expects to place absolute trust in his orchestra leader. He explained something of the complexity of conducting, where "hundreds of decisions, second upon second during a performance" have to be made instinctively and instantly. Runnicles expects the leader to be his eyes and ears, picking up on every changing nuance and subtletly, and ensuring that all of this is transmitted – whether by gesture, playing style, glance or whatever – to the rest of the orchestra.

More than that, he has to know the leader, and she him, so intimately that she can almost second-guess what he's going to do. Runnicles expects nothing less than the leader should effectively be able to read his mind and, through infinite familiarity with his style, anticipate what he wants.

Laura Samuel is an amazing player. As second violinist for many years in the Belcea Quartet she was a rock, with her impeccable playing and her ability to counterpoint the more volatile, and sometimes harsh, edgy playing of first violinist Corinne Belcea. Last year she guest-led the SSO in a tough contemporary piece at the Edinburgh Festival, and her prowess, strength and power as a leader were very striking, as I remarked at the time. This looks like a seriously good appointment.