David Cameron has launched a defence of the United Kingdom as his government prepares to put the "facts" about Scottish independence to the public.
While people in Scotland will make the decision in autumn next year, the implications will have obvious impacts across England, Wales and Northern Ireland, the Conservative leader said.
"Britain is admired around the world as a source of prosperity, power and security," he said.
"Those glorious Olympics last summer reminded us just what we were capable of when we pull together: Scottish, English, Welsh, Northern Irish, all in the same boat - sometimes literally.
"If you told many people watching those Olympics around the world that we were going to erect barriers between our people, they'd probably be baffled. Put simply: Britain works. Britain works well. Why break it?"
Cameron spoke out one day before the government publishes the first in a series of analysis papers about Scotland's role in the union.