This does not contain practical advice, so it is not a self-defense tip but a statement of fact.
Last weekend in London three murderers killed 7 people and injured 48, of which 21 critically. The attackers drove a car into a crowd and then proceeded to knife people.
The attack lasted 16 minutes.
Police arrived eight minutes into the attack and it took them another eight minutes to kill the attackers.
None of the attacked people was allowed to have a baton or pepper spray or any other defensive weapon. That is the law in the UK.
London police is very proud of its very fast response. Really.