How to spot an extramarital affair: Those close to Petraeus saw the early signs

Petraeus and Broadwell at the time of the biography (AFP PHOTO / ISA)

In the wake of David Petraeus's resignation as head of the CIA over revelations of an extramarital affair, John Barry in The Daily Beast says the signs of Petraeus's infidelity were there for all to see.

"By that last year in Kabul, it was clear to all who saw them that the pair had established a close relationship," writes Barry. Signs included the couples habit of taking early morning runs together and Broadwell's "transparent admiration" for the subject of her book.

"Relationships between senior male officers and some trusted female staffer were once fairly commonplace, " Barry adds. "There are limits to what a commander can talk about even with the most trusted subordinate. So it's not uncommon that a female staffer becomes a more-or-less permanent fixture on some star's personal staff: the trusted listener."