A Royal Naval destroyer had been in shipyard and was leaving the jetty for sea trials. Back then the wheelhouse was below the bridge and the type of telegraph required a 360 degree rotation to advance the order to be transmitted. There were only stop, slow ahead, half ahead and full ahead with the corresponding divisions astern. At half ahead the ER obeyed the revolution indicator, the same astern.
The port engine was at half ahead and the starboard engine half astern when the order was given slow astern. The young sailor on the telegraph wound it the wrong way and a cotter pin fell out jamming it.
Full ahead or full astern means all you have got, danger to human life and damage to machinery accepted. The bridge were trying to communicate with the ER over the sound powered telephone over the rising noise from machinery and command seeing a collision with a stone breakwater aft announced " close all red and blue openings, stand by for collision aft." Unbeknown to the command both the boiler room and the ER heard this clearly through the newly fitted speakers and as the inquiry said redoubled their effort to achieve full power astern on the starboard engine.
Collision was the word used as Jolly Jack is generally unaware of the distinction.