Has David Cameron started to worry that he might actually lose the EU referendum?

I have just returned from David Cameron's rooftop press conference in central London.

And I came away from it thinking one thing: the Prime Minister has started to worry for the first time that the UK might just vote to leave the EU.

You might call it panic. You might say he's fretting. But it shows Mr Cameron and the Remain campaign are on the defensive - perhaps for the first time in this campaign.

There have been polls which show Leave just ahead. It feels like the Leave campaign have had the momentum ever since those immigration figures two weeks ago when Mr Cameron was at the G7 summit in Japan.

Today, Mr Cameron accused the Leave team (and we should be clear that the team includes members of his own Cabinet) of lying, of peddling mistruths, of making false assertions.

In fact, the prime minister said he called the press conference 'after watching last night's news' in order to reassert the warnings to the economy of a Brexit.

Today he referred to three interventions: the warnings from Janet Yellen of the Federal Reserve, the boss of Hitachi and the World Trade Organisation. They have all - in various ways - talked of the economic & trade pain of leaving the EU.

But it also suggests voters have heard that message often enough and have instead - in the last week or so - connected with the issues of immigration, the EU budget and other messages being hammered out by the Vote Leave campaign.

Of course, Leave voters are more likely to vote than Remain voters. Therefore, in a not dissimilar way to the independence referendum in Scotland, voters may need to be told how tight the race is in order to encourage them to vote on June 23.

But I saw a worried David Cameron behind that lectern today.

He has a primetime TV appointment on ITV tonight in the hope that the message will stick.