If this was a US ship I would guess the reduction gears. It's a massive gearbox which basically is like the automatic transmission on a car. I don't know if the Brits use the same setup, I'm guessing they probably do.
It needs to be tweaked perfectly. Sometimes it takes a few efforts to get it just right as the ship goes through it's testing and operation phases.
If this was a US ship I would guess the reduction gears. It's a massive gearbox which basically is like the automatic transmission on a car. I don't know if the Brits use the same setup, I'm guessing they probably do.
It needs to be tweaked perfectly. Sometimes it takes a few efforts to get it just right as the ship goes through it's testing and operation phases.