Not enough. This may be sentencing by guideline, but this case calls for exemplary sentencing. The victim had serious injuries. We could see from the tape shown on TV that injuries were inflicted with intent to cause grievous bodily harm; maximum life imprisonment. We have had cases like this before and there is reason to believe that they are not unusual.
The principal offender should have got 12 years, and let the Court of Appeal sort out the inevitable appeal. They can't interfere, as the Crown won 't appeal this sentence as too lenient, but, with 12 years they can lay down rules for cases such as this, which may well mean more that less than 7 years not being appropriate.