Keendog. You're probably right. I recall being on duty when a certain lady politician went out of Heathrow some years ago. In her typically charming way she had issued instructions that once she was aboard the plane must start and taxy immediately and from the time it started to move it was not to stop - presumably to "conserve" fuel. Unfortunately she was quite a bit early... so it started as soon as she was aboard and we then had great fun routing it all around the airfield to waste 15 mins until it's slot time.