Leak found!

After some head scratching, the suggestion that the leak was coming from the oil pressure gauge turned out to be correct.

Opened up the dash and there amongst a rats nest of cables was the tube leading to the gauge, with not one but three different holes in it. All look like they had been touched with a soldering iron.

I guess the misfire the other day with the pops and bangs it had shocked the pipe enough to finally crack.

The next task is trying to fit the barbed insert back into the shortened pipe, boiling water isn't quite hot enough and the heat gun is too hot.

I shall have a go at making a clamp block to use to hold the pipe secure while I apply some percussion to the   insert.