This challenge is simple, you start in a base and choose a direction and distance to be teleported away from that base.
Then all you have to do is return to the base, however, the world border will chase you all the way at a speed of your choice and will damage you if it catches you, the amount of damage dealt is again decided by you back at the base. You also decide how much of a head start you have against the border.

Should the border catch you it is game over, if you are on multiplayer, you will be placed in spectator mode unable to win, you will remain in this mode until there is a winner or every player has died and a new round can begin.

Please note that if you start the world in spectator mode, you will have to enable cheats to return to adventure, I'm not sure why this happens and am looking for the cause. Also, if the border timer does not count down, press the reload redstone button back at the base. The control panels are numbered, you MUST use them in the order 1-6 else you may break the redstone.

Because there are so many permutations of distance, direction and speed, I have not been able to test all of them, if you are finding a particular setting difficult, it may be impossible, feel free to edit the redstone systems under the base to suit your speed.

If you wish to post a video, you have my full consent provided you credit me in the description and/or the video.

Anyone who wins with the following settings is a legendary borderman!

Distance: 10,000 blocks
Border Speed: Almost sprinting
Border Damage: Instant death
Head Start: 100 ticks.

Thanks and have fun!
You must be in 1.8 for this map to work correctly.