Well spotted.. it does have two cables. One is the original cable which pulls the throttle linkage. The other is connected to an electric servo mounted behind the passenger seat. This is operated by a switch on the steering wheel. When we restored the car for the present owner, he had very restricted movement in his right foot and could not toe and heel, Hense the servo operated blipper.
Infact it worked so well I used it for the whole of my 2 hr stint at the Spa 6 hr race.. but dont tell anyone.
Send me a PM if anyone needs a period exhaust system.
A.