"I am doing my absolute best to not look triumphant today," said Mr Salmond following the signing of the agreement that will fulfil the Scottish National Party's 80-year-old ambition for a referendum on independence.
With most polls currently indicating that a minority of Scots want independence, Mr Salmond has two years to persuade them them to back his vision. "Just as I believe in independence, I believe in the ability of persuasion on this argument," he said.
Mr Cameron said he will be arguing to keep the United Kingdom "family" together.
"Now we've dealt with the process we should get on with the real argument," he said.
The Edinburgh Agreement states that the referendum should have "a clear legal base; be legislated for by the Scottish Parliament; be conducted so as to command the confidence of parliaments, government and people; and deliver a fair test and decisive expression of the views of people in Scotland and a result that everyone will respect".