Having been a trustee, I'm irrevocably prejudiced in favour of them.
I think the kind of people who get involved in charity trusteeship are generally more caring and compassionate than the average. And therein can lie a problem.
Trustees have responsibility for the overall running of their charities, but they can often end up mentoring peers, helping junior colleagues with career progression or helping staff with their development in a whole range of ways.
It can be hard to say 'no', especially when being a role model and being a trustee should never be mutually exclusive. But not being clear about responsibilities and boundaries can cause problems in the boardroom.
It can be hard to hear criticism of a protege's report recommendations without hearing it as criticism of the protege themself. This makes it hard to evaluate the contents impartially.
It can also be difficult for fellow trustees to raise concerns about the performance of staff you mentor, or about board work you don't seem to have time for.
Managing expectations can be tricky. Boundaries are notoriously messy, and it's easy for others to forget which hat you're wearing - friend or trustee - when you undertake official business.
Your priorities and boundaries must be clear. You are there as a trustee.
Mentoring can be a really effective way to improve staff or peer development - if your charity has staff, ask for this to be put on the agenda at a forthcoming board meeting and, with your fellow trustees, work out the resources and organisation needed to set it up.
Organisations such as the NCVO and many community foundations offer guidance on mentoring. If it's worth doing, it's worth doing well to maximise its impact.
You can make a huge impact on your charity - but only if you recognise that your priority is being a trustee.
• Rosie Chapman is executive director of policy and effectiveness at the commission