"Her warning to Cameron was this: only if treaties had to be renegotiated could there be a vote for them," Kornelius wrote. "And a vote was likely to turn out badly – of that Merkel was certain."
Even then, Merkel worried about the possibility of the U.K.'s "accidental exit" and about Cameron overplaying his hand after misinterpreting her warnings. Kornelius wrote:
Merkel also had another fear: Cameron might misread her signals and take advantage of the hard line that she was adopting with the crisis-hit countries, as well as her sympathy for his demand for a repatriation of powers. If the British prime minister insisted too much on these demands, then ultimately she might be the only one who would be able to keep Britain in the EU. Cameron might exploit the fact that the Germans wanted to keep Britain in the EU at any cost, because it suited their interests. But Merkel doesn't like veiled threats. If it reached that stage then she would decide whether the price was too high, and if in doubt she would decline.
Cameron knew all this as he was negotiating his February 2016 EU reform deal that preceded the referendum. He just believed Merkel would give him more concessions on the EU's freedom of movement rules and other exceptions from EU treaties in order to keep the U.K. in the bloc. When the compromise she helped him get fell short of Brexiters' expectations, he still went ahead with the referendum. Even when the vote didn't go the way he'd hoped, he continued believing in a deal that would keep the U.K. in the common market without freedom of movement.
In his memoir, Cameron revealed that at his last European Council meeting on June 28, 2016, Merkel told him the hopes had been futile. "Angela Merkel assured me we wouldn't have got any more in the renegotiation," Cameron wrote. But he still didn't believe the Europeans meant what they were saying, and accepted empty flattery from European Commission President Jean-Claude Juncker.