Boris Johnson: Intelligence questions raise trust issue again
Can he be trusted? It's the first question we asked Boris Johnson when he eventually took questions at the start of this campaign.
The questions that many of his colleagues aren't quite sure about. And of course, the question that the front runner to become prime minister in a few weeks answers heartily, yes of course.
But when it comes to the most sensitive matters of state, maybe it is not quite so straightforward.
There were issues about the sharing of intelligence with Boris Johnson when was foreign secretary, particularly in his first few months in the job, sources have told the BBC
It is understood that Theresa May and some in the intelligence community had worries about his ability to keep information confidential.
And the tension went back as far as the time when he was Mayor of London and she was home secretary, when one source claims he angered her by inadvertently revealing confidential information before it was due to be made public.
Once he was in government, on occasion Downing Street would even convene smaller meetings, or "pre-meets", to discuss sensitive subjects rather than include him as foreign secretary, a senior figure has told me.
You can read my colleague Gordon Corera's full story on what happened here.
Mr Johnson's campaign team denies there was ever a problem while Mr Johnson himself has said it is "not true" that anything was withheld.
But one of his allies confides "it was obvious there were concerns on issues from early on" and suggests "there was a constant question of whether he was really seeing everything" - the full intelligence picture that he would be entitled to in his role as Foreign Secretary.
It's said that he worried constantly about being cut out. But, this is not just about the keeping of secrets, but Theresa May's desire to keep political control.
It's suggested that the real issue was a lack of trust and hostility between Mr Johnson and Theresa May. One source believes Mr Johnson was excluded from seeing some sensitive information because there was a hostile relationship between him and Downing Street, not because of reservations from the intelligence services.
And they suggest that despite early doubts among the security services about him, they eased over time and by the time he left his post, they had good relations.
Another senior figure closely involved at the time blames a mixture of factors for the situation, citing Mr Johnson's perceived lack of discipline, nervousness among the intelligence community, and hostility between him and Theresa May.
Ballot papers have now started landing on Tory members doormats. These revelations aren't likely to dim the zeal of some of Mr Johnson's ardent supporters.
He is one of an unusual breed of politicians who is admired, perhaps as much, because of his flaws as despite them.
But for those who doubt him, it's another area of concern, another tension any new prime minister could ill afford.