The Prime Minister launched into a brief argument for Scotland remaining as part of the UK after the Scottish referendum in 2014.
He said he believes the case for union can win the "arguments of the heart" as well as the "arguments of the head".
He said he is proud of what the UK has achieved together, such "defeating fascism" and the NHS and BBC.
But he also drew attention to the more than 12,000 people in Scotland employed by the defence industries, which he said were backed by the whole of the UK.
More top news
The Syrian city of Raqqa has been liberated from Islamic State militants, a senior commander for a US-backed force has said.
Paranoid schizophrenic Jeffrey Barry stabbed Kamil Ahmad before removing his penis in the attack at his flat in Bristol last year.
The latest addition to the royal family will be a younger brother or sister for Prince George and Princess Charlotte.