The short answer
They differ in who the obligation runs to. Director coaching creates a private obligation to one person. Board advisory creates an obligation to the company. Mentoring creates no formal obligation at all. Confusing them is not a semantic problem — it produces conflicts that cannot be unwound once they exist.
That is why retained board advisory is not offered here, while director coaching is.
The three, separated
Director coaching. A confidential one-to-one engagement with a person who sits on a board. The client is the director. The content is theirs. The obligation — including confidentiality — runs to them, and to no one else. Nothing said in that room reaches the company, whether or not the company is paying.
Board advisory. A retained relationship in which someone advises the board, or the company, on matters before it. The client is the organisation. The advice becomes part of the company's decision record. The obligation runs to the company.
Mentoring. An informal relationship, usually unpaid, usually open-ended, in which someone more experienced makes their judgement available. There is no engagement letter, no defined outcome, and no fiduciary dimension. It is valuable and it is not a service.
Why the distinction is load-bearing
Put coaching and advisory together and you produce a person who holds one party's confidences while owing the other party advice. There is no protocol that makes that safe.
The concrete version: a director is being coached, privately, on how to handle a disagreement with the chief executive. The same coach is retained by the company to advise the board on succession. The coach now holds material information from one side of a conversation they are being paid to shape from the other. Nobody has behaved dishonestly, and the position is already untenable.
This is why the two engagements here are kept apart and stated as such: an appointment as an independent director, or coaching an individual director — never both into the same company, and never a standing advisory service dressed as either.
The conflict rules, stated plainly
Ambiguity here is worth more to a competitor than to a client, so these are the actual boundaries.
Not permitted: coaching a director of a company where I hold a board seat. The private obligation to the individual and the fiduciary obligation to the company cannot both be honoured.
Permitted: coaching a director of a different company in the same sector as a board I sit on. Sector is not a conflict; a shared boardroom is.
Permitted: coaching a director of a company that competes with one where I hold a seat — because the coaching room contains the director's own development, not their company's confidential strategy. If an engagement began to require the second, it would be the engagement that stopped.
Permitted: coaching a director who sits on the board of a former client. The First Discipline does not expire when an engagement does, and it runs in both directions.
Checked at the point of nomination, not screened in advance. There is no standing conflict list, because whether a conflict exists depends on the company in front of you.
What this means if you are choosing
If you want someone to help a person think — a director who is new, or stuck, or heading into a difficult succession — that is coaching, and it should be confidential to them, including from whoever pays for it.
If you want someone to help the board decide — on strategy, on a transaction, on governance design — that is advisory, and you should engage someone who does it as their practice. Asking a coach to do it, or a coach offering to, means one of the two roles is being compromised.
If you want neither, and simply want access to judgement, ask for mentoring and expect it to be informal.
The commercial honesty in this
Declining retained board advisory costs revenue. It is a service organisations ask for, and the request usually arrives from someone already in the room for something else.
The reason to decline it anyway is that the alternative is a practice where clients cannot be sure which hat is on. An independent director's usefulness rests entirely on the credibility of their independence, and a coach's usefulness rests entirely on the confidentiality of the room. Both are destroyed by the same compromise, and neither is recoverable once it is.
Limits
This describes how one practice draws these lines and why. Other practitioners draw them differently, and some jurisdictions and listing regimes impose their own independence tests that are stricter than anything described here. Nothing on this page is legal advice; a board considering whether an engagement affects a director's independence should take its own.