G'day

New member here, I just joined the club and bought a 93 Defender 200tdi that's been sat in a paddock for the last 5 years, reported to be a good runner before being abandoned.

Yesterday I brought it back to life, but... there's a gas leak

It's coming from the back of the motor, somewhere near where the block and head meet (right in the centre) it feels like exhaust gas escaping, I really hope it's not the head gasket, I've already replaced 2 in the last 12 months on my daily vehicle (don't ask)

Here's a short video of the leak
The engine seems to be running fine but without having a proper look I'm not sure what's going on, I'll take a mirror and torch next time I go work on the vehicle.
I really hope it's not another head gasket! but I have a history of bad luck with them

Any idea what could be going wrong back there?
Ben.