After the Telstra NTS issue and preparing for the upcoming summer storms and power outages, I set up a chrony mesh on three devices, each with a different upstream stratum 1 NTS. I seriously considered a GPS reference too, but I live on the bottom floor of apartment blocks so reception is probably quite poor. After blocking the firewall ports, the mesh stays linked and drift is well within sensible boundaries for the typical length of internet and power outages of a few hours. Although, a man with a watch knows the time but man with two watches cannot be certain.