These little beauties are well worth a go. I read somewhere else that Marcella learnt this from her assistant - probably 50 years ago. Well, they are still tasty.
It's important with recipes to read the instructions carefully. Marcella once said cooking times bored her, because it might take 3 times as long on your stove than hers. It depends on the heat, and what's being cooked, no doubt among other things.
I ended up cooking these for over an hour - maybe 70 minutes, until her description was matched and the meat came away easily from the bone.
Worth the wait.