At 05:18 this morning nagios notified me of a failure of one of the two power feeds in Servology rack 2 at Telehouse North. The ATS in the rack reported a loss of redundancy (but as far as I can see, the input which failed was the one it was not using at the time, so it did not need to switch), and several servers with dual power supplies reported one of their two PSUs had failed. I contacted Star Europe and one of their staff discovered that a circuit breaker had tripped and switched it back on at about 07:15. This restored redundancy and I believe this problem is now resolved.
This does leave the question of why the breaker tripped. I’m not sure there’s much I can do on this front as the Star staff member couldn’t see anything untoward, but if it trips again I will have to find a way to investigate.