Managed to catch up with walk-thru owner on sunday and asked about your engine. He has very kindly lent me his workshop manual which covers perkins engines that were in walk thrus - four 192 & four 203.
This is where I get to sound very knowledgeable when really I'm just quoting the manual.
Perkins engines have an engine number stamped in 2 places - one on camshaft tunnel next to fuel pump and the other on the opposite side near the fuel filter.
Engine block looks like this
Diagram for cold starting only show one cold start device which seems to confirm possibility that if yours is a perkins walk-thru then it has been modded
Mansel was saying that could have been possible as perkins were really bad starters - he had one in a truck he drove where he would need to start up at 4AM and the only way to get the fleet of them going was to put a petrol soaked lit rag down the inlet to draw the fire through engine (dragging bits of lit cloth through at the same time, made an interesting noise apparently). Once the first one had fired then it was used to drag start all the others. So it could well be that yours was driving someone potty enough to stick some extra plugs in.