Security wall around Buckingham Palace

There was no line to get in, and Buckingham Palace was still open to the public (the State Rooms and Gardens) since the Queen is still in her summer residence in Scotland.  This is not a museum but a living, working house of state.   Opulence, power, majesty is evident in every part of the building..
No photos allowed, but when I left, I couldn't help catching this outside wall.  And although the barbed wire is saying something, it seems like minimal security for such an important site.