Even if Thomas Knyff's will can't be found, based on the information in this and other threads, it looks like we have a fairly good biography for him:
- born about 1450, the son of John Knyfe, of St Sepulchre, corser (horse dealer) and Matilda/Maude (will 1469)
- son in law of John Cowey of Islington, married to either Agnes or Elizabeth (will 1476)
- lived in Islington through the 1490s (Common Pleas)
- died by 1508, probably a couple years before that. The case in Common Pleas is somewhat involved and had probably been going on for some time. So, say, died in 1506.
London. Command to the sheriff to take goods that had been of Thomas Knyff, of Iseldon, Middx, gentilman, in the hands of William Darset, of London, gent, and Richard Bayly, of St John Strete, Middx, yeoman, executors of Thomas Knyff, both for a debt of 10 marks which Thomas Ryche, of London, mercer, has recovered against them, and for 36s 8d damages for non-payment of the debt.
http://aalt.law.uh.edu/AALT2/H7/CP40no983/bCP40no983dorses/IMG_0795.htm