The problem with the modern diesel is the large torques that are produced, this will quickly set a clutch to smoking, and sometimes destroy the clutch altogether.
Slipping the clutch is the main culprit, along with excessive revs. This is easily done. I had a primera smoking on a hill start, the audi quattro smoking on a slight slope trying to get onto a busy single carriage way, revs and slipping the clutch in both cases.
There has been many posts on here about burning clutches while reversing. I often think the brake override may not be working correctly, or the brakes are over adjusted. You are not aware of the power the car is giving out, i have actually set of with the motor mover engaged with the xtrail, the car did not "feel" right, that's all that alerted me!
The answer is to fit a mover, consider it an investment, transfer it to the next van etc, and it will pay for its self.
I will never tow without one, we couldn't physically push our van, and i find reversing a chore.