Influence without authority comes from trust. Build relationships and offer value to other teams before you need their help. When you do ask, frame it around their goals, not yours.
Look for: building relationships before needing them, understanding others' priorities and constraints, finding shared goals, using data to make the case, offering help before asking for it, and leveraging formal and informal networks. Best candidates discuss specific examples of driving change across organisational boundaries.
Critical leadership skill at all levels. Most important work crosses team boundaries. Candidates who can only lead within their direct team will struggle as they become more senior.