Cigar shaped green light moving slowly through the sky

I was van camping with one other friend in the top carpark at Bigbury-On-Sea (what3words exact location… ///reporting.stored.deduced). I was on my laptop in the back of the van with my friend, it was around 11 or 12 at night when my friend opened the side door to go to the toilet. He immediately shouted to me “Quick shooting star!” I hastily climbed to the door to see, when I noticed immediately that it was not a shooting star it was moving far too slow for that. I shouted to him “that’s not a shooting star I think that is a UFO” I quickly jumped back in the van to grab my phone to take a picture or video but by the time I had grabbed my phone it had gone and there was nothing to be seen. (I’m not sure my camera is good enough quality to pic it up anyway as it was very dark outside). We looked around and listened for a good 5 minutes to see if it reappeared or see where it went but it had vanished with no trace. My friend had a much better look at it and for longer than me. I estimate that I only viewed it for no longer that 5 or 6 seconds.
It was a very clear night with very little cloud cover, no wind or rain but there was some very light wispy clouds dotted around the sky. The object had just entered some low clouds it appeared like a cigar shaped off white light with a green glow, moving completely silently slowly forward. It was completely symmetrical and appeared about an inch to inch and a half long moving forward in one direction.
My first thought was UFO but being slightly sceptical about these things I tried to rationalise it. I ruled out Starlink as it was far to short and stubby and it was to big to be satellites. My next thought was an aircraft’s headlight being projected through the clouds leaving a glow similar to a cars headlights in fog. But the light was very defined and there was no aircraft sound, silhouette or an aircraft at the back also there was no anti-collision bacon or port and starboard lights flashing at all. The cloud was to thin this would have been visible and at the altitude that it was we would have heard some engine noise.
I am an Aviation, Firefighter and I work around aircraft. I’ve never seen a UFO before and I know what aircraft in the air look like. I didn’t have any phone signal at the time as I wanted to check on flight tracked to see if an aircraft had just passed to rule that out. I checked the next day and aircraft do come close to that spot on rout from Europe to Manchester Airport. But in my opinion this was very unusual and not an aircraft. I can only give the facts to what I saw and I would not report it if I thought there was a chance it was just a plane.
My friend got a much better look at it for longer than me and he said that it looked like it was ribbed. He explained it as almost Caterpillar like. I cannot comment on that as I can only say what I saw.
I’ve tried to do my best to illustrate it but my art skills are not very good.