what they are doing is outthinking you. put yourself in their shoes. if i just pull on this lead rope a little more each time, i can train this human to incrementally do less and less each time to get ahead of me, and pretty soon, they will leave me alone. all it takes is the reward of getting left alone when i do something bad is the only taste the need to keep trying. it's like the cookie jar for kids at 3:30. parents wait till the kid has one hand in the cookie jar, and the other with a cookie in their mouth and then they punish them.
this is what i would do at this point.
make small little pulls with a very very long lead rope, that is about 3 feet shorter than the diameter of your pen. if you calf wants to pull, NEVER NEVER let him pull on anything, just drop the lead rope with one hand, and if he takes off, big deal. gather him up, and only approach him if he is stopped. you are not training him to be a bucking horse, which is probably essentially he has become to some extent. you need to work on both sides of this calf. make little pulls and hold them, and let him put the slack in the rope, and then scratch him on his favorite spot. some animals like to be scratched between the inside top of their legs, between their front legs, and between their shoulder blades, and aboout 6 inches behind their polls and behind their ears.
gradually make the pulls translate into getting his feet to move. work both sides. working on the off side gets him used to other people, such as say a judge or a competitor or a audience member leaning over the rail.
when an animal that likes to take off engages their rear end, their inside rear leg is always stepping in front of their other rear leg when going in a circel. if you get them to make that step BEHIND the ooutside leg, you are disengaging the engine. then pet. he needs to know that park is a good place to be. the more you quit on a good note the better.
think about it, if you think about this like every time this is a date with the same gal or guy, and it always ends on a bad note, yet you have no escape, more and more time is going to be spent on trying to get that date to leave you alone. it's like saying your but is big instead of saying , you know i had a good time, do you want to go out tomorrow too?