give us some background on that, n nic. >> reporter: it does absolutely. the mayor should focus on crime in london. this came to a head following one of the terror attacks on london where president trump made comments about that attack. kahn pushed back at the time, president trump doubled down on his criticism of kahn following that. the two do have form on their differences here, but again, arriving into the uk with that tweet, taking on the mayor of london, it does divert away from some of the criticism that has been labeled and directed at president trump for wading into the brexit debate here, the leadership debate here, and of course it takes away from other issues that are going to sort of dot their relationship albeit, you know, with the prime