I expect this is a policy primarily aimed at Wales and Scotland, given the last year has seen all 4 nations acting almost autonomously from one another on the biggest crisis in decades and the obvious issues surrounding support for independence.
There's bound to be disassociation from the British state when everything major is coming from Holyrood and the Senedd, and I presume their press conferences have been in front of the saltire and the red dragon.
It will be part of a campaign to try a rebuild support for a British identity and the United Kingdom
Obviously Northern Ireland has been excluded because of the history and issues there, and the worry of inflaming violent tensions.
I may be giving people too much credit, but I really don't think it's just to try and distract voters in Norwich from the failings of government by waving a flag from a building.