What is this Queensland lizard/dragon, and is it friendly or dangerous? [closed]

I've spotted quite a few large lizards around Brisbane's parks, such as in Roma Street Parklands. Today, while I sat in a park by the river, one scuttled over. I took his photo, then he pushed himself up high showing off his red chest, and looked distinctly unhappy about me being there.

At this point a gaggle of German tourists spotted him and ran over to take his picture, which caused him to make a dash for the nearest bush. I therefore didn't get to discover first-hand if he (or she!) was dangerous or not.

The FourSquare page on Roma Street Parkland has quite a few tips about these, calling them variously lizards and dragons. Some seem to suggest they are friendly, others that they're dangerous, but I'm not sure if all of these entries are serious.

Does anyone know what kind of lizard / dragon / reptile these are? And from that, if they're dangerous or not?

In case it helps, here's a slightly closer photo of another one I came across a few days ago: