It is alleged, that Michael Gordon Peterson, aka Charles Bronson, (b.1952), dubbed "most violent prisoner in Britain" and "Britain's most notorious prisoner", claims, via the semi-autobiographical film Bronson (2008), that he was at HMP Manchester [Strangeways] during the riot and that he is seen, in the above film in actual news footage, wearing a balaclava-mask sat performing his trade-mark V for Victory sign.
Due the Victorian era toilet-less cell made Prison one factor for the riot was the practice of slopping-out. This was the emptying of buckets left in the prisoners' cells that were used as toilets. Prisoners had to empty said bucket in the morning and this practice was called slopping-out.
The abbreviation HMP, when placed in front of a UK prison location, stands for Her/His Majesty's Prison, depending on the relevant gender of the presiding Monarchy; examples are HMP Lincoln or HM Prison Wormwood Scrubs.