I didnt do it! Parkers did...
Its probably possible but not real world driving whatsoever.
In my T5 I can get it to give me a constant(ish) 35-37mpg @ 56mph, but that isnt "real world" driving. I normally average 18-22mpg. Same goes for my 1.4 16V Clio, I got that to do about 55-60mpg at that speed, although the average is usually between 40-45mpg!
I would imagine that parkers wouldnt rely on the fuel computer, as they are often out by a fair margin on most cars and wouldnt give a good comparision.