Sometimes we are asked to act only for the other firm. If our advice is generic (i.e. we don't know the ultimate client's identity, or there may not be one and we are dealing only with the other firm), then we can act only for the other firm. In this case, we would need to caveat that our advice is based only on the instructions we have received and we do not assume any liability to any client of the other firm. If they want to use our advice as part of their advice to one of their clients (and where that advice would be attributed to us, rather than held out to their client as their advice), then we should suggest they come back to us and allow us to check it can be used for that purpose/amend it so it can be. That, in turn, would require a new direct retainer with the ultimate client who is the recipient and beneficiary of our advice. You would also need a direct retainer where you can clearly work out the identity of the end client with some certainty. If that is the case, you cannot say you don't know the end client and you can be sure that the end client can make a credible argument, if things go wrong, that we owed them a duty of care. For these reasons, you will need to be properly and directly engaged by that client.