Scotland Yard said a man had been arrested on suspicion of causing grievous bodily harm.
Three men have been arrested on suspicion of causing grievous bodily harm.
The jury took just under two hours to unanimously clear him of causing grievous bodily harm.
The alleged attacker in Saturday's stabbing has been detained on charges of attempted murder and causing grievous bodily harm.
Jaymin Abdulrahman was cleared of attempted murder and causing grievous bodily harm with intent to her six-day-old daughter.
Michael Broom, 50, was originally sentenced to three years in prison after admitting causing grievous bodily harm to Mark Haley.
He was questioned on suspicion of three counts of murder and various counts of causing grievous bodily harm.
Teresa Gilbertson, 60, a former special constable from Peterborough, appeared at Peterborough crown court on Tuesday for sentencing after being convicted of causing grievous bodily harm with intent.
At the Old Bailey in December 2015, teaching assistant Kevin Wilson, 23, was convicted of child destruction and causing grievous bodily harm to Malorie Bantala.
In April, Nazrul Islam, 16, of Upton Park, east London, was jailed for 10 years after pleading guilty to causing grievous bodily harm with intent.
When the driver was finally charged six months later, it was only with dangerous driving causing grievous bodily harm to me.
