I'm feeling the need for some moral support, however, so I'm going to randomly open Sir James Frazer's The Golden Bough and see what it has to tell me.
Okay, here's what I've found:
"Old men may eat tortoises freely, because having already lost the power of running they can take no harm from the flesh of the slow-footed creature."
I'm really not sure how this information will help me out, but one can never tell what the future holds. Just to be on the safe side, however, I'll randomly open a volume of Samuel Pepys's diary and see if that illuminates the tortoise quotation at all.
"My wife having dressed herself in a silly dress of a blue petticoat uppermost, and a white satin waistcoat and white hood, though I think she did it because her gown is gone to the tailor's, did, together with my being hungry, which always makes me peevish, make me angry, but after dinner friends again."
Possibly she served him tortoise?