The assailants were convicted of violent disorder which is a public order offence. They were not convicted of assault, which is an offence against the person. I don't understand why, CPS guidance says that where they meet the thresholds for both they should be prosecuted for both, or in some circumstances, assault only.
The threshold for violent disorder is 3 or more people using or threatening unlawful violence such that 'a person of reasonable firmness' present at the scene would fear for their personal safety.
By prosecuting a public order offence rather than an offence against the person, the victim disappears. They weren't convicted for the harm they did to this young person, they were convicted for scaring the public while they were doing it.
Sentencing guidelines appear roughly similar for both offences. There may be technical reasons why it was better to go for the public order offence on its own. IANAL so if there's a reason it would be great if someone could explain because this was very obviously an assault against a person.
According to CPS guidance this attack also meets the threshold for ABH. PP implied that it didn't because the victim only sustained severe abrasions and a black eye. My layperson's reading is that while the actual injuries sustained by the victim are relevant, there are other factors to take into account, e.g. where there has been 'significant violence' or where there has been 'punching, kicking or head-butting'.
Sentencing guidelines for ABH include 'Use of weapon or weapon equivalent (for example, shod foot ...' as an aggravating factor. Also 'Intention to commit more serious harm than actually resulted'. I've seen the video, we all have. The victim was lucky that the assault happened in such a public place and was stopped quickly.
Clearly they should have dragged him out of the tube station and into a dark alley before kicking the shit out of him.
www.cps.gov.uk/legal-guidance/public-order-offences-incorporating-charging-standard
www.sentencingcouncil.org.uk/offences/magistrates-court/item/violent-disorder-2/
www.cps.gov.uk/legal-guidance/offences-against-person-incorporating-charging-standard
www.sentencingcouncil.org.uk/offences/crown-court/item/assault-occasioning-actual-bodily-harm-racially-religiously-aggravated-abh/