The UK Government's periodic role as an honest broker between the Northern Irish parties is now needed again. It has a duty - to the heroic, courageous moves towards peace on all parties in the recent past, and to the people of Northern Ireland now and in the future - to be and to appear impartial. And this is why the Conservative-DUP deal is so concerning. Any UK Government formally reliant on any Northern Irish party simply cannot be seen as the honest broker it needs to be. The Government really should abandon the idea of a formal deal. They are playing with fire. And the stakes are too high to risk it.