[strider]

Car started first turn of key but appeared to have a slight judder. After 200mtrs engine management light started to flash. Pulled over and turned back home with engine management light on permanently and cruise light flashing approx every 1 sec. Any suggestions would be welcome.

 

[plain OM]

The CEL flashes when there's a problem with the engine that is considered "serious" and can harm the engine or emissions system. The cruise control is automatically disabled when the CEL is on, thus the flashing cruise light.

No telling what causes the CEL without reading the trouble code or codes that would stored in the engine control module's memory, but it could be something like a cylinder misfire.

On some years it's possible to read the codes from the instrument panel; others require an OBD code reader. Perhaps indicate information about the car (year, model, engine, transmission, mileage, recent work done, major service schedule items completed, and where you are, and we'll try to fill in more details.

 

[strider]

Thanks OM I think it is the ignition system that is causing the fault. Seasons Greetings.

 

[Corvison]

Had this happen to me on a FL road trip. Engine shuttered at idle and CEL. Codes thrown for O2 Sensor (inferred, I can't remember the code)
Local Subaru Dealership found a intercooler hose leak/uncoupled. Replaced the hose and connectors, and reset for about $70. Perfect since.

Hope that helps.