Is this not the same tactic that was used in Scotland some years ago? Thank God there was no detonation.
Yes - Glasgow Airport 2007 - on the face of it does look somewhat similar but we don’t have many details yet
Actually it harkens back further than that: the 1983 Beirut Marine Barracks Bombing. Here is a link to the Wikipedia article on the bombing and the pertinent portion dealing with the nature of the bomb:
https://en.wikipedia.org/wiki/1983_Beirut_barracks_bombings
“The explosive mechanism was a gas-enhanced device consisting of compressed butane in canisters employed with pentaerythritol tetranitrate (PETN) to create a fuel-air explosive.[9][10] The bomb was carried on a layer of concrete covered with a slab of marble to direct the blast upward.[39] Despite the lack of sophistication and wide availability of its component parts, a gas-enhanced device can be a lethal weapon. These devices were similar to fuel-air or thermobaric weapons, explaining the large blast and damage.[40] An after-action forensic investigation by the Federal Bureau of Investigation (FBI) determined that the bomb was so powerful that it probably would have brought down the building even if the sentries had managed to stop the truck between the gate and the building.”
However, the Sydney attacker got it wrong in that you need high explosives to provide the energy the gas will enhance, and burst the cylinders to begin with.
However, setting yourself on fire and crashing the car probably should receive some points for improvisation.