Mot - direction arrows on tyres

[Lee]

My friend just had not fail for rotation arrows wrong direction, but they change tyres around or something and passed it, charge £10..

If you have rotational arrow on tyres, does this mean spare is only good for one side??? Or for temp fix only or what's the score?

Never heard if this before, but seen the "outside" and "rotation" markings but never gave it a second thought.....