Multilateral Bargaining - It is always dangerous to have separate, bilateral meetings when trying to get a collective agreement involving three or more parties, although often necessary. For the unwary and inexperienced it is easy to get picked off by more expert and prepared negotiators.
Having a private meeting with one party when there are up to 28 parties to the deal, can lead to making a concession unilaterally to each one in turn to gain each as an ally. All of the 27 other Premiers might ask for a different condition in return. This could lead to 27 concessions (favours) being made for just one gain. Using up considerable currency in a very inefficient manner. And if the deal does not happen, the other parties now know of 27 possible concessions that they might (should demand) gain during the next negotiation.
Buying favours to build up alliances can lead to secret agreements that are “called in” later as part of other deals. An ever present danger.
It is one thing to have informal discussions to “get a feel” as to how things might go in the formal negotiation - what interests and concerns the other parties might have, but to go beyond the preparation and investigative dialogue stages will be a step too far.
Once one has the “intelligence” gathered in, then comes the time to construct powerful proposal options which will bind in all the parties. This approach maximises the efficiency of one’s trading currency, but needs plenty of practise and experience.