Obviously the most apparent symptom would be a very hard brake pedal that requires considerable pedal pressure to achieve the desired braking effort.
I suspect there might be another, less visible symptom:
The relevant thread starts here : Plugs as found in the car, before the servo diaphragm was diagnosed as torn
New plugs after less than 1000km driven with torn brake servo diaphragm:
New plugs after < 1000km
Talk about the E-Type Series 1