It's hard to argue against the fence around Parliament House in Canberra, because we don't know what the security agencies advocating it know, and they won't tell us.

We can note, however, that the proposal for a 2.6-metre fence around the national Parliament's perimeter has been met with dismay. Additional security measures for the building have been rushed through both houses in the closing sessions of the year; the fence is expected to be erected over the summer.

Hundreds rolled down the lawns of Parliament House to protest against the fence proposal. Credit:Rohan Thomson

It seems children will no longer be able to roll down the celebrated grassy slopes; nor will joggers be able to bust their guts sprinting up them. But we don't know exactly what it will look like, because the blueprints are being kept under wraps as a matter of national security. Nor has the justification for the security upgrade been adequately explained.

That leaves it to leading architects like Glenn Murcutt to declare the security upgrade a "knee-jerk reaction".