Perhaps it was starring in a Bond film
The 321s as built had LCD front displays, just like the 158s. Could this mean that they had the same destinations programmed?
720s down Turkey Street aren't the rarest things in the world. During stupid o'clock (or during diversions) trains sometimes go via Seven Sisters via the Weaver Line (including Turkey Street) instead of the regular route via Tottenham Hale. Or, it's an ECS move that runs via that way, which again isn't the rarest thing in the world.
They're not all that rare, especially on diversion... but this one was a bit odd. It ran as 2Z04 non stop to Hertford East (except what looks like a stop to wait for a gap at Theobalds Grove). Bring back GA calls to Edmonton Green, I say... They'd be chuffing handy in a morning!
My best guess is that it was done to give an extra service from Hertford East later on. Although why it was just one five-coach unit, I'm not sure. Perhaps its usual partner is getting painted in the new livery? Waiting at Theobald's Grove makes a bit more sense, as it probably needed to wait before it could use the Cheshunt junction.
