Guards can be found around the Anachronia base camp, defending it, and in Varrock Dig Site before travelling to the island.
The one north of the base camp can be talked to or right-clicked to view the Anachronia Agility Course records: the player's fastest lap time and total number of laps completed. The guard also provides an option to reset player's lap progress.
This information has been compiled as part of the update history project. Some updates may not be included - see here for how to help out!