wˌɛn hɪz fˈɜːst kˈʌzən bˈɑːnɪfˌeɪs, kˈaʊnt ʌv sɐvˈɔɪ dˈaɪd ɪn wˈʌn θˈaʊzənd tˈuːhˈʌndɹɪd sˈɪksti θɹˈiː, ðə fˈɪftiːnjˈɪɹˈoʊld tˈɑːməs ɹᵻɡˈɑːɹdᵻd hɪmsˈɛlf æz ðə səksˈɛsɚɹ ʌvðə dᵻsˈiːst, ænd klˈeɪmd ðə kˈaʊnti ænd ðə hˈɛdʃɪp ʌvðə hˈaʊs.
When his first cousin Boniface, Count of Savoy died in 1263, the 15-year-old Thomas regarded himself as the successor of the deceased, and claimed the county and the headship of the house.