MPs, if a person was to genralize, have humanity degrees. This is not the best background for making judgement calls on scientific data. Having a spad like Dominic Cummins to reach to the nitty gritty is invaluable. Several oil companies I worked for brought in facilitators to bring a focus to specific problems and their solution. Their function can be summarised thus:
    Design and plan the group process, and select the tools that best help the group progress towards that outcome.
    Guide and control the group process to ensure that the above objectives are met.
    Ensure that outcomes, actions and questions are properly recorded and actioned, and appropriately dealt with afterwards.(ie lead the "lessons learnt" process)
I would see the role of Dominic Cummins as being broadly comparable to that of a facilitator. One single person able to bring a focus to disparate threads and guide/control the decision making process.
The few facilitators I encountered were geeky and super smart.