Is the 45m rule for fire fighting access in buildings not fitted with fire mains measured from the outside or from the front door?

Guidance in both volumes of the Approved Document Part B states there should be vehicle access for a pump appliance to within 45m of all points within dwellings. This is to take account of the actual distance that the Fire & Rescue Service need to carry kit and lay hoses from the vehicle to a potential point of fire.