Road blocked beside US Embassy

Concrete blocks across Upper Grosvenor St tonight beside the US Embassy, shutting road and making it very hard to access Park Lane coming from Bond Street. Real pain. Anyone know if they are temporary or permanent?

Should be temporary, must be related to the recent attack. Worst case it will stay there until autumn when the embassy moves out.

I came into work around lunch and was stopped by police on Victoria Embankment escorting a long convoy of black cars with dark tinted windows making their way through towards Westminster.  Also The Mall was closed up and barriers down only letting traffic out so I had to go around through Pall Mall.  Up until St James street there were at least 20 police on motorcycles waiting around.  Must be something big on!