Possible Clues:

• The policy of being a part not apart
• It favours staying part of the UK
• A policy of those who want to Remain presumably advocated by the politicians up north?
• Principle of some labor groups
• Perceived worry in industry -- for the nobs wanting awkward minions kept under?
• Civil War doctrine
• Principles of those opposed to secession
• Policy opposing to separation
• Policy of TUC or some Northern Ireland politicians