Appearances on the progamme
Tassier achieved five centuries in his octochamp run, including a top score of 120, although he also achieved two scores in the 70s. He finished 5th in the seed table.
Tassier's results set up a quarter-final with No. 4 seed John Hardie. In a high scoring game, Tassier prevailed 122 – 107 thanks to the nine ADDICTIVE. In the semi-finals, another nine, OUTBRAVES, swung the pendulum in his favour late on as Tassier defeated No. 1 seed Thomas Carey to set up a final with Jonathan Wynn. The final went to a crucial conundrum, however neither player solved TTHESCORE and Tassier was defeated by 4 points.
Championship of Champions XV
Tassier returned to Countdown to participate in Championship of Champions XV in January 2019. He played Dougie Mackay in the third preliminary round of the tournament, breaking away to achieve a 96 – 78 thanks in part to his six-small prowess. In the Quarter-final he took on Tom Chafer-Cook, where he was overwhelmed by Tom’s word knowledge and lost 111 – 62.
Tassier is a numbers expert, some say the best Countdown numerist in the world. Obviously he practiced on Apterous, and held the record for the extremely hard Spoilage numbers attack for six years before being beaten in 2020 by Dave Robjohns by just 4 points.
In 2013, Tassier achieved an incredible feat when he was able to beat the Apterous computer, and therefore beat the max, on a Hyperlock Numbers round. 
|#||Date||Type||Contestant 1||Score||Contestant 2||Guest||Lex||Max|
|6245||9/11/2015||P||Keith Kan||65 – 102||Matthew Tassier||Michelle Collins||Susie Dent||141|
|6246||10/11/2015||P||Matthew Tassier||98 – 24||Tam O'Hare||Michelle Collins||Susie Dent||124|
|6247||11/11/2015||P||Matthew Tassier||77 – 65||Romaine Boothe||Michelle Collins||Susie Dent||131|
|6248||12/11/2015||P||Matthew Tassier||110 – 26||Bob Lowe||Sherrie Hewson||Susie Dent||146|
|6249||13/11/2015||P||Matthew Tassier||120 – 26||Eoin Jardine||Sherrie Hewson||Susie Dent||135|
|6250||16/11/2015||P||Matthew Tassier||103 – 57||Sarah Bladon||Sherrie Hewson||Susie Dent||124|
|6251||17/11/2015||P||Matthew Tassier||114 – 48||Chris Kiely||Sherrie Hewson||Susie Dent||134|
|6252||18/11/2015||P||Matthew Tassier||75 – 51||Jim Anderson||Sherrie Hewson||Susie Dent||112|
|6274||18/12/2015||QF||John Hardie||107 – 122||Matthew Tassier||Tim Rice||Susie Dent||146|
|6275||21/12/2015||SF||Thomas Carey||94 – 104||Matthew Tassier||Tim Rice||Susie Dent||153|
|6277||23/12/2015||GF||Jonathan Wynn||98 – 94||Matthew Tassier||Tim Rice||Susie Dent||130|
|6982||4/01/2019||CP||Matthew Tassier||96 – 78||Dougie Mackay||Kate Humble||Susie Dent||135|
|6990||16/01/2019||CQF||Matthew Tassier||62 – 111||Tom Chafer-Cook||Jon Culshaw||Susie Dent||128|