Ultimately Australia's Failure To Control Itself Is Australia's Fault.

https://news.sky.com/story/sydney-mall-attack-bollard-man-who-confronted-knifeman-offered-citizenship-by-australian-prime-minister-13116403

However I don't think anyone would be surprised if the shared Monarch were to issue a clear & concise apology on Britain's behalf.

It must be very traumatic for Australia.

Watching a longstanding ally continue to flatly refuse to make any attempt to improve its situation.