99-year-old Peter Bartrum has been compiling Welsh genealogies since 1929. He's just donated his 26 published volumes, covering the years 300 to 1500 AD, to Aberystwyth University, which will put them online over the next three years.
Mr Bartrum, who is from London and has no family ties with Wales, handed his work over to the university recently.
Prof Gruffydd Aled Williams, head of the Welsh department, said Mr Bartrum's work "was an important source for academics and historians".
"It makes it possible to identify a person's lineage, his period and region with a minimum of effort, work which would otherwise take months of researching original manuscripts," he added.
"In theory, anyone who can trace their ancestry back to the 16th Century should be able to go back much further thanks to Dr Bartrum's work." [Link]