This photo (via BBC), of Angela Merkel, David Cameron, and Barack Obama taking a walk during the G7 summit in Germany, dates from just over 16 months ago. At that time, Cameron had just won a general election, the Republican party was about to experience the ostensible reality TV sideshow candidacy of Donald Trump, and Angela Merkel was in the process of opening the door to what would turn out to be 1 million refugees.
Who looked the most politically threatened at the time?
There's a huge amount of hindsight certainty (and its counterpart, "if only ...") going around. Nothing is ever so clear in real time.