Apaches patrolling the Thames

[CoastGuardJon]

Hi all, a bit late now, but I was in London for a meeting Wednesday 19th January in Westminster area, and was more than somewhat surprised to see and hear Apache helicopters patrolling the Thames.   Does anyone know if this was just a one off - why? Or is this becoming a regular feature.   All around HoP metal anti-vehicle barriers (almost anti-tank type, secured with special security bolts) were being installed and literally hundreds of Met. Police around - rumours were that another "student" (my reading "anti-establishment anarchists") protest might be in the offing, but this seemed a bit OTT for that.