One such case was resolved this week when I was looking for the background to Tommy McInally, a Celtic star forward of the 1920s who also had spells at Third Lanark, Sunderland and a few other clubs. He won two caps in 1926, against Ireland and Wales. Known as a maverick who delighted the fans, he died of alcoholism on 29 December 1955. There were obituaries in the press, and an inscription on his grave at St Conval's Cemetery in Barrhead. But if you check the death registers, Thomas Bruce McInally, as the reference books call him, is nowhere to be seen.
However, there was indeed a McInally who died that day, but his first name was Bernard. Death certificates give the names of parents, and from there it was simple enough to find the birth certificate of Bernard McInally, born in Main Street, Barrhead on 18 December 1899 to Francis McInally and Anne (maiden name Slaven). By the time of the 1901 census the boy was recorded as Thomas, the youngest of eight children including his older brother Arthur, who also went on to play for Celtic. And, for whatever reasons, he was known throughout his life as Tommy until that final note of his death reverted to his 'official' name.