ATCO 4 STROKE ENGINE - NO STOP SWITCH EVER FITTED

Dad is restoring a 1959  Atco "4-Stroke"  14"   with the ATCO VILLIERS AV3 Engine.  (An adapted Villiers MK7)

The Villiers Mk7 had an air vane Governor, like on a Suffolk engine.  The Atco-Villiers AV3 engine doesn't have a Governor, which is not an issue as lots of cylinder mowers (like the Dennis Premier)  do not.

The engine doesn't have a stop switch / stop button / spark plug cut out, like on other Villiers Engines, so what would the engine cut out procedure be?

I can assume having the Villiers S10 Carburettor, stopping procedure would be just to retard.