Gertrude is spot on, I should have added that.
It may be of interest also that it is the policy of Essex County Fire & Rescue Service NOT to cancel appliances once they are responding to a call, whatever the circumstances, they always continue so they can decide for themselves (additonal units responding can only be cancelled by a 'stop message' from a unit on scene that has assessed that further resources are not required)
I believe this policy was adopted years ago after they did cancel and the incident they were attending 'went wrong', so to speak.