1S25 (North Highlander) seems to have had a slight issue...
It left Euston on time (2028) with 87002 leading to take it as for as Wembley for the reverse (ECML diversion tonight) - but appears it hasn't even made it to Camden Junction yet (20 mins later). Pendolinos are also heading away from Euston on the Up Fast, suggesting 1S25 is blocking the Down Fast (which it was on) - or something else is blocking the line and it's stuck behind it.
Update:
Now looks like it's back in Platform 15 at Euston (and Pendolinos etc have resumed on the Down Fast) - most likely dragged back there by the 92 on the rear (that's there ready to take the train forward from Wembley).
The poor passengers on 1S25 will be very confused tonight - Euston to Camden, wait for c.20 mins, then back to Euston; Euston to Wembley, wait for c.30 mins, then back to Camden...
Further Update:
On it's way again, this time on the Slows... 87002 leading after a short time back at Euston, so presumably not an issue with the traction - perhaps something wrong with the stock (air leak or similar), or an external factor?