The Sydney City Council thought it was a good move to put concrete
bollards into Martin Place to stop terrorist truck attacks.
That is fine as far as it goes but the fire brigade insisted that
there had to be a gap between them to enable a fire engine to pass through.

Hmmm, does any one else see a problem there ?
No comment anywhere about that.

The obvious solution is to have at least one of the bollards able to be moved out of the way. I've seen folding bollards elsewhere in Australia, and overseas I've seen automatically retracting bollards.

One of the most effective barricades used, has been council water trucks, filled of course. Appear to be an effective and quick mobile solution when required for special events. The water is also useful afterwards. Unfortunate for council, they have had to bear the cost of labour, with no funds from state or federal. For some it is appreciate if the security costs, which often are substantial, should be passed on to the organizer of special events. What do others think?

Aiden, I have seen the retracting bollards also.
Folding bollards I have not seen. How do they work ?
Anything that could be moved by hand or pushing by truck would not be
much use. These concrete blocks need a large forklift to move them.
I presume that is why the holes are in them.
So a gap that is large enough for a fire engine to get through will
let anything a terrorist turns up in through the gap.

Yes Bazz. Australian politicians are "really that stupid".

Bazz,

They're hinged at the base, and padlocked. Once the padlock is removed, they can be folded down by hand.

The ones I've seen probably wouldn't be strong enough to actually stop a truck, but they'd certainly put a dent in it, slow it down a bit, and then noise of them being struck would provide a significant warning to pedestrians. And most importantly, they'd be a visual deterrent for anyone contemplating such an attack.