Elan Plus 2 Headights Not Working

The main headlights on my 1968 Elan +2 don’t work but full beam does work. I had the same fault a year ago but it then went away.

Presumably I should check the earth connection first. Does anyone know where this is located? There seem to be 3 wires connected to the chassis near the engine mount. Could it be one of these?

Any advice much appreciated.

Could try cleaning the contacts on the light stalk first.