The historian Emma Mason suggests that Hamo, along with Ranulf Flambard, Urse d'Abetot, Robert FitzHamon (Haimo's son), Roger Bigod and Eudo Dapifer, were the first recognizable Barons of the Exchequer under William II [REF].
Hamo was still witnessing royal documents in September 1099,[REF] and was one of the witnesses to the letter which King Henry I (1100-1135), William II's brother and successor, wrote to Anselm, Archbishop of Canterbury, shortly after his accession [REF].