No thanks Simon. You can RTFM and then try to tell us what it says. Let me know when you give up.
The iPad is one of the most sophisticated computing platforms yet, despite it's seeming simplicity. Why would you not think to read the manual for it?
The laziness of some people astonishes me.
I disagree, the location of the rotation lock is hardly intuitive in iOS 4.2. Just one example of many.
That would be why they have a manual for the device.