Interesting one I’ve never seen before - but yesterday’s 4454 from RTM to LCY was cancelled. Flight had fully boarded, about to go when it was notified that there was some concern over the ‘ratio’ of the fuel (renewable:fossil) used in the plane wasn’t as expected. ‘luckily’ they hadn’t started the plane yet but seemingly Shell went to ground, they blamed BP who supplied it and no one wanted to confirm anything so it wasn’t risked.

also affected a transavia plane fuelled at the same time - so now there’s 2 planes sat at RTM that may be there a while pending further investigations.

i was on the later flight, BA seemed to handle
it well and got everyone on my flight but the cafe/restaurant there also decided to shut the kitchen to the delight of everyone with catering vouchers 🙄