Morning update: fears were not fully founded, it is thin-ish, but defo thinish marmalade (which tastes damn good). Marmalade and jam are different animals, at least I cook marmalade to several degrees higher than I would jam, which would result in a potentially lethal napalm mix in the microwave. Never underestimate the power of molten sugar.
My fear stemmed from a failure a couple of years back when I tried a recipe that said "put all the pith into the muslin with the pips" as a result, the pectin didn't get out the parcel; I had an excellent substance for making marmalade cake but spreading was right off the agenda. This time, apart from pressure on time causing me to say "ah bugger it it's done" I used normal as opposed to preserving sugar. That meant I had much more scum than normal, which was setting damn solid and adding to the pressure to stop cooking. As I said, nobody to blame but myself.
Anyway, all's well that ends well. The Waitrose organic sevilles are top on flavour.
