Yer as i said in the earlier post the 'burden of proof' is on the prosecution, and there are specific ways in which police are trained to get readings of speed ... if that evidence that you did '183km/h' is proved to be completely false (which it most definitely is) then the case for you speeding could get thrown out altogether, or at least reduced to some lesser charge that they *can* prove.
'burden of proof' means that *they* (the prosecutor/police/whatever) have to PROVE that you were doing what they are charging you with, you don't have to prove anything you just have to cast enough doubt on the evidence that *they* provide (and that will usually include you presenting your own evidence). So for example you don't need to provide evidence that you were obeying the speed limit, you just need to provide an argument or evidence that will either disprove, or cast doubt over, any evidence/'fact' that the prosecutor presents - i.e. that you were doing 183km/h.
So if say the policeman got a reading off his radar, and you could prove that it was erroneous - then the only way you could get charged with anything is if the cop had made other notes/documentation about the incident like speed relative to his car/speedo if he was following at a fixed distance, statements that you made for example if you had said you thought it was some skyline wanker that you wanted to ditch etc ... it doesn't look good for him to change his argument in court and present facts of the case which conflicts with other facts. If the policeman doesn't have any other numbers aside from 183km/h anywhere in his records then his case is quite fuxed. A good lawyer will be able to help you out, it sounds like this cop has pulled a number out of his arse without following procedure and is not doing his job particularly well.
You *could* still get charged with other things like excessive speed, dangerous riding etc - it all depends what the cop has noted and what you said to him on the night. If you are ever in this situation again, just remember you don't have to incriminate yourself ... you aren't in court so you don't have to reply to anything, or make any statement if you don't want to. It's not like i'm suggesting that you try and be a prick and get away with everything ... just don't feel like you have to be 'guilty' and admit to every little sin
Note : i'm not a lawyer, a lawyer will know a bit more about the legal precedent set in these kinds of cases and will have a better idea about which way to go with the situation ... i'm just making some very broad generalistations that may or may not give you some ideas.