Lemass never left any papers or an autobiography. Instead, he gave 22 hours of interviews to an Irish businessman Dermot Ryan in 1967 and 1968. The transcripts were given to The Irish Times and extracts from these interviews were published as a supplement in May 2018.

They laid bare tensions in his relationship with long standing Taoiseach de Valera, his disdain for the IRA, his complicated relationship with Great Britain and much more.