"Thankyou for that information, that was darn helpful!"
While I was peacefully doing the November HE review H asked me where East was on his screen. There is a graphic of the relevant bit of a rotating compass. I was able to explain that the bit in the middle indicated the direction he was facing right now.
So I'm now stuck with lots of memories of those floating compasses on gimbals lit up somehow as I steered a compass course at night across a portion of the Channel.
I don't remember any ferries so I must have been given part of the journey between the 2 shipping lanes.