Thanks to you all for previous advice. The mystery of the cat poo on the lawn has been solved. Not a cat but a fox. His card has been marked. Have apologised to all the local cats for miscalling them lol.
Makes you wonder how many cat haters have been wrong about the poop on their lawns before! I have never owned a cat that would do that anyway, maybe bury it in flower beds, but never just on a lawn.