If the team's own leader won't show leadership, nothing you do will matter. Sorry to be a downer, but that's my experience. No amount of away days or team building sessions will create any lasting change because everyone knows that they aren't being actually held to account for doing anything different.

If this team's behaviour is going to affect the C-leader's own KPIs (and, therefore, their bonus or pay rise or whatever) then they will pay attention. If the team's behaviour is going to get the C-leader in trouble with the CEO or Board and potentially risk their job, then they will pay attention. But if their C-leader will face no consequences from the dysfunction of their team then nothing is motivating the C-leader to get involved and nothing will change.

In reply to Robey:

And in fact the C-Leader may use the dysfunctional team as a "sink" for all issues to be blamed upon.

It needs sorting top down not bottom up

Hi Alys

I’d suggest some form of exec coaching for the c leader. I’ve provided similar for middle leaders and whilst I have ‘authority’ I need them to own their problems - even if they don’t realise it is their problem.
It’s almost like a failure of duty of care by the c leader and i’d focus on bringing them to realise it. The consequences could be significant if ignored.

In reply to Robey:

Thanks all - those are really helpful thoughts and I do agree. It's been really quite frustrating and feels like an ongoing battle. I plan on raising this with the CEO this week. I do like the idea of exec coaching - I'll see how that suggestion goes down.