What do they look for when they check the tyres in the MOT (safety and maintenance test) ?

Question from visitor, 08/01/2010 :What do they look for when they check my tyres during an MOT test? What would make my vehicle fail the test?
Answer by rezulteo, 08/01/2010 :

Your vehicle may fail the MOT if your tyres have one or more of the following: a significant tear, tread depth of less than 1.6mm, different wear on the same axle, damage (lumps, bulges, distortions) incorrect tyre size or 2 tyres with different brands on the same axle.