Urban plunder at Marlborough House?

Until May this year each of the two entrances to historic Marlborough House were complemented by an elegant period lantern surmounting each pillar . .

They have now disappeared from both . . .

 . . . and from the way the wires have been left one fears the worse.

Security has recently been tightened at the site . . .

Have the conspicuous notices announcing this fact have merely served to alert thieves to an opportunity?