Whatever it was, it reversed itself at ~11o/c.
It's happened a couple of times recently (showing on both IPv4 and IPv6, no loss of PPP, sometimes a small red spike), my guess is a routing change somewhere that (after a while) is reset. Maybe for maintenance purposes or something.
nearly two and a half times that of your FTTC connection
18mS is high for my my connection. It's usually ~9mS, but shortly after Christmas the DLM took it into its pointy little head to put me on interleave again, and hasn't taken me off it yet
It usually takes me off fastpath for a few months around this time of year for some reason