^ This.
Armed Response officers wouldn't have been involved in the stop as a matter of routine, they would have been present either due to intelligence regarding the vehicle / occupants (most likely), or (very unlikely) just because they happened to be close by. In the event of the latter, they would have been alerted to the suspicions relating to the vehicle / occupants before executing the stop for reasons of their own safety.
On the subject of the threats to police officer Martyn Blake and his family, it's worth remembering that it was Kaba's family who campaigned extensively (and ultimately, successfully) to have him named instead of him maintaining anonymity as would be normal in cases such as this (for obvious reasons), while simultaneously taking out an injunction to have Chris Kaba’s criminal activities kept private.