Its back now but no idea what I did - I followed TTTs instructions and got as far as 'stretch' but nothing happened then I managed to move it over to the left so I could see the bit at the top right that I pressed and it suddenly expanded.
I have no idea what a data cable is or does? It was like I had pressed the minimise button but because it was so far over to the right I couldn't get to the maximise button to reset it - somehow managed to move the picture over to the left but again not sure how.