The exact quote, from Mr Justice Jacob in Sony v Owen, is

"The fact is that if you spoil your CD, which has a recording of music on it, you have to go and buy another. The same is true of a CD carrying a game. Backups are not necessary at all."

Now you might quite reasonably consider this to be a completely daft ruling that only a judge that has never used a computer could come up with - and, academically, the judgement in Sony v Owens is considered rather flawed - but until a higher court overrules this interpretation of s.50A of the Copyright, Designs and Patents Act, he is stating the law in the UK.

There is commentary elsewhere suggesting that backup of tape and floppy disk would be permitted (although AIUI it was said 'obiter dictum', i.e. it is not binding). UK law is not exactly up to date in this area..!