Geoff,
Well, the (my extremely) helpful Rootschatter has indeed been to the Lincoln record office today and looked at that 1798 John DOCKERY will, and your intuition was on the bull's eye!
He leaves everything to his housekeeper, a Mary KNOWLES, mentioning his two "natural" children Susannah DOCKERY and Peregrine KNOWLES (with the name DOCKERY later added). So, I'm now trying to disentangle exactly what might have been the sequence of events. But, quite clearly, John DOCKERY had rather more of an interest in Mary KNOWLES than just her dusting and cooking...
I'll PM you shortly, to see what you might make of it all, as you fairly obviously very much have your finger on the pulse of Lincoln records...
What fun this has all turned out to be!
Regards, Keith
Sorry, I stand corrected - in the John DOCKERY 1798 will it's Peregrine DOCKERY, with KNOWLES later inserted..