Duval made his debut on 6 November 2018 against Chris Sturdy. He won the game on a crucial conundrum and went on to win with another crucial conundrum on his second day. He also outran his opponents thanks to his preferred 3 large and 3 small number picks during the numbers rounds. In his last game, he ran ahead early but his opponent Lewis Jones made a strong comeback by spotting the nine letter word TELESCOPE, which Duval missed as he had the six letter word CLOSET. However, Duval outran Jones and became the seventh octochamp of the series. He was ranked No. 6 seed, for the series finals in December 2018.
When the New Zealander returned for the series finals, he was pitted against No. 3 seed Andrew Jackson. The pair fought hard with Duval taking the lead early on but Jackson fought back, thanks to his number skills and eventually took the lead. However, the game eventually went to a crucial conundrum, and Duval, who was 8 points behind, successfully unravelled EVENDURST to take the win and played in the semi-finals.
In his semi-final, he was pitted against No. 2 seed Mike Daysley. The pair started level until the second half when Duval took a seven point lead thanks to a tricky 1 large numbers game. However, in the third half, Duval slowed down and eventually Daysley ran ahead and solved the conundrum, and Duval took his first defeat.
|#||Date||Type||Contestant 1||Score||Contestant 2||Presenters||Guest||Lex||Max|
|6946||6/11/2018||P||Chris Sturdy||80 – 84||Alan Duval||Nick Hewer||Rachel Riley||Colin Murray||Susie Dent||130|
|6947||7/11/2018||P||Alan Duval||68 – 67||Bethan Lycett||Nick Hewer||Rachel Riley||Colin Murray||Susie Dent||122|
|6948||8/11/2018||P||Alan Duval||82 – 63||Rich Murray||Nick Hewer||Rachel Riley||Colin Murray||Susie Dent||119|
|6949||9/11/2018||P||Alan Duval||93 – 40||Peter Wilkes||Nick Hewer||Rachel Riley||Adrian Chiles||Susie Dent||121|
|6950||12/11/2018||P||Alan Duval||89 – 41||Ian Kennedy||Nick Hewer||Rachel Riley||Adrian Chiles||Susie Dent||132|
|6951||13/11/2018||P||Alan Duval||82 – 19||Lisa Skidmore||Nick Hewer||Rachel Riley||Adrian Chiles||Susie Dent||124|
|6952||14/11/2018||P||Alan Duval||87 – 64||Jane Capie||Nick Hewer||Rachel Riley||Adrian Chiles||Susie Dent||135|
|6953||15/11/2018||P||Alan Duval||89 – 62||Lewis Jones||Nick Hewer||Rachel Riley||Adrian Chiles||Susie Dent||133|
|6975||17/12/2018||QF||Andrew Jackson||60 – 62||Alan Duval||Nick Hewer||Rachel Riley||Phill Jupitus||Susie Dent||131|
|6978||20/12/2018||SF||Mike Daysley||97 – 69||Alan Duval||Nick Hewer||Rachel Riley||Phill Jupitus||Susie Dent||121|