Cameron is stating the belatedly obvious. Merkel helped cause Brexit.
In his final meeting with EU leaders before standing down as Prime Minister, Mr Cameron claimed that British voters backed a Brexit because people believe the country has “no control” of its borders. Setting out the basis for a future British deal with the EU, he said Britain would only be able to maintain access to the single market if the bloc agreed to look again at its policy of open borders.
Good luck with that.
Merkel dug the EU into this hole which helped make Brexit and then perhaps Frexit inevitable. The end result can be thought of as a German victory only in the same pyrrhic sense as WW1 and WW2. Germany gets Eastern Europe. Turkey gets Germany. Arguably you can see a straight line from WW1 to this thorough disaster from the idealistic rhetoric about a world without war through unity to Germany's deadly flirtation with Islam and the Ottoman Empire.