Back in the day, Prime Minister Robert Menzies was fond of taking solitary walks around Old Parliament House.

And he travelled to work in an unguarded car, with an unarmed driver.

How things change (but some stay the same).

What would Sir Robert think if he was still around to see an Australian Federal Police officer carrying a rifle at the front door of Parliament House?

Or the metal detectors screening visitors, or the current PM riding in a bulletproof limousine, with an AFP close protection vehicle riding shotgun?

In 1953, the Melbourne Argus lamented the lack of security surrounding Sir Robert, after a person was detained carrying a knife near the PM's office. However, it added: "Admittedly history has shown the risk to be slight."

Australians are used to seeing their political leaders in shopping malls during election campaigns, but the media does not publish the location of such "street walks" beforehand.

It was curious, therefore, when John Howard was holding a roadside press conference in North Queensland during an election campaign, that a local wheat farmer knew where to find the PM. Or perhaps he just stumbled on the gathering.

The man, clad in shorts and grimy work shirt, walked briskly into the media circle, unhindered by police, and dumped a bag of flour at the PM's feet to make a point about government subsidies.

An AFP officer explained later the man was not halted because he had the right to protest in a democracy and the threat level was low because he was assessed as not carrying weapons.

That was before the rise of al-Qaeda but, even now, the cowardly terrorists prefer "soft" targets, such as civilian-filled market places.

Around the world, security agencies are being funded to tighten cordons around political leaders, hence the changes to entrances at Parliament House, the presence of armed police and the planned fence at the ministerial entrance.

In a robust democracy such as we enjoy in Australia, the current upgrade to security at Parliament House must balance the security requirements with the openness and accessibility expected of the parliamentary institution.

And luckily, Tony Abbott still has the freedom to ride his bike in Canberra's pre-dawn darkness