EWAN Angus is one of the most experienced broadcasting commissioners at Pacific Quay, the BBC's headquarters in Glasgow. His CV as commissioner and executive producer reads like a list of most of the major non-news productions made by the corporation north of the border in the last 20 years. His most high-profile success, Still Game, was the most watched show in the nation last year.

That is perhaps why it seemed a common-sense move for Mr Angus to be in charge of creating and leading the new BBC Scotland channel, the as-yet un-named service which will be broadcast from next Autumn.

Now, with the sudden announcement of his departure, he will need to be replaced.

The BBC also needs to find someone who can follow in his footsteps as an experienced and knowledgeable commissioner of new comedy and drama.

Meanwhile, the planning of the new channel is ongoing, and Mr Angus will be key in that endeavour until he leaves.

The plan is moving along two roughly parallel tracks.

First the BBC must put its case together for the Public Interest Test: a series of consultations with "stake holders" have already taken place (including with newspaper editors). "Quantity and quality" analysis and other measures are assessed, and are then are presented to the BBC Board.

If that process is deemed to be sufficient, the details of the new channel are given to Ofcom, the BBC's new external overseer, which will then mull the plans for around six months. It is expected that Ofcom's decision on the new channel will come in March, 2018.

At the same time, BBC Scotland is preparing plans for the new channel's editorial output. This is where Angus' departure leaves a question mark. The creation of a new channel from scratch is a "huge undertaking", insiders says.

We know there will be a new hour long news programme in the evening: but what else will it broadcast? And who will be the new journalistic faces on board? These are unlikely to be hired until the new year, I am told. Around 80 will be brought on board, the corporation says.

Mr Angus' influence on the new channel will end within months. The job of Donalda MacKinnon, director of BBC Scotland, in creating a new channel for Scotland just became a little bit harder.