Showing my total ignorance of what I am supposed to see in a routing table, but mine includes something I don't recognise and I want to be sure there's not something misconfigured somewhere. The table looks like this (WAN IP anonymised):

S 0.0.0.0/ 255.255.255.0 via 192.168.30.1 VPN-1
* 0.0.0.0/ 0.0.0.0 via 172.16.15.71 WAN1
S 86.129.X.X/ 255.255.255.255 via 86.129.X.X WAN1
C~ 192.168.1.0/ 255.255.255.0 directly connected LAN1
C 192.168.30.1/ 255.255.255.255 directly connected VPN-1
* 172.16.15.71/ 255.255.255.255 via 172.16.15.71 WAN1

What I don't understand is why there is a 172.16.X.X address in there as I don't use 172... anywhere. Is this 'expected behaviour'?

..and you may mercilessly rip the p1ss out of me if this gets dumb question of the day award.

On mine the * (default route) corresponds to the gateway IP of my ISP (shown under Online Status > Physical Connection) except mine is a public IP. I don't know if that helps?

I think I was being even dumber than I originally thought -it seems that 172.16.15.71 is the BT gateway address per my Online Status page. I was confused thinking that the 172 subnet is the same as the 192 subnet, ie for internal use as opposed to being an internet IP.

Interesting that your gateway can be a private address. I guess I never considered that the connection between one’s router and ISP isn’t using the public internet.