How British coastal motor boats launched torpedoes astern

How did British coastal motor boats launch torpedoes during raids such as Kronstadt?

They dropped the torpedo from a stern trough and turned away while it accelerated forward along the boat's previous course.

The coastal motor boats associated with the 1919 Kronstadt attack used a simple stern-launch arrangement rather than a heavy trainable tube. The armed torpedo was released down a trough at the back of the boat. Its propulsion engaged as the boat peeled away, leaving a clear path toward the target. A delay or gradual run-up reduced the chance that the weapon would catch the launching craft, making the arrangement light and mechanically reliable for a very small attack boat.