Yes it was. And that was the officer's justification for taking the £200 there and then. There was no indication given to him that he could challenge the allegation or what the process would be if he did.
As I said, this may have been edited out. But I'm not so sure that it was because when the driver's initial attempt to pay failed, they directed him to a customs shed (or whatever it was) and actually clamped his vehicle. They warned him that it would remain clamped until the penalty was paid.
I'm not at all sure they have the power to do this. I've looked at Dover Harbour's bylaws and there seems to be nothing about road traffic offences at all. Unsurprisingly they are all to do with boats and navigation and the like. In any case, I doubt that bylaws would give them he right to demand payment and not offer the driver the opportunity to have a court hearing.
Strangely, when I first saw this it was the matter of whether the ramp is a road or not. But on reflection, I think a far more important aspect is the demand by the police for payment of a fixed penalty.