The Special Patrol Group was an "élite" division of the Metropolitan Police force formed in 1961. To quote the Met's own website:
The Special Patrol Group Unit was organised in 1961 to provide a centrally based mobile squad for combating particularly serious crime and other problems which could not be dealt with by local Divisions.
The convenient presence of a disciplined, well-organised team brought the Group into increased use for the control of demonstrations, where their presence sometimes came to assume unwanted symbolic significance.
What this actually means is that the SPG came to regard themselves as above the law, and in an era before modern techniques of riot control were used in the UK, the SPG were often used to violently control anyone perceived as a threat to public order. In 1973 they were responsible for shooting dead two Pakistani youths holding hostages with replica firearms and in 1979 they bludgeoned Blair Peach to death during an anti-Nazi protest in London. The subsequent outcry, particularly from the ethnic minority communities in Britain, led to the SPG's ultimate disbandment.
In the early 80s in Britain the SPG was synonymous for police brutality and all that people perceived to be wrong with the police force; this is why in The Young Ones Vivian called his psycopathic killer hamster "SPG". | 
