Such was Young Master Vaughan's advice when I checked on my sourdough starter this morning. In spite of the cautionary advice, I took a quick sniff and didn't think the smell was as offensive as yesterday. Vaughan wasn't taking any chances though!
I spooned out about half the starter and discarded that portion for composting. I then added more flour and water to the jar, stirred well and tucked the starter back into the thermal cooker. I'll check on it again tomorrow - and do a bit more research about sourdough baking in the meantime.