He opened his account with 4 wins in the last games of Series 51 before the series finals. Thirlwall's only century was in his debut game on 8 June 2004 against two-time victor Mark Hannon, when compiling a 102 – 95 scoreline.
Thirlwall's record of 704 points meant he returned as #7 seed for the finals, running into Jack Welsby in the quarter-finals. Thirlwall never really seemed to find his 'A' game this time around, the 93 – 58 scoreline in favour of Welsby ending the career of Thirlwall.
|#||Date||Type||Contestant 1||Score||Contestant 2||Guest||Lex||Max|
|3718||8/06/2004||P||Mark Hannon||95 – 102||David Thirlwall||Richard Stilgoe||Susie Dent||130|
|3719||9/06/2004||P||David Thirlwall||95 – 52||Jane Coulon||Richard Stilgoe||Susie Dent||134|
|3720||15/06/2004||P||David Thirlwall||77 – 67||Eric Robinson||Martin Jarvis||Susie Dent||131|
|3721||16/06/2004||P||David Thirlwall||88 – 55||David Phelan||Martin Jarvis||Susie Dent||129|
|3729||28/06/2004||P||David Thirlwall||96 – 89||Martin McGuinness||Gyles Brandreth||Susie Dent||134|
|3730||29/06/2004||P||David Thirlwall||80 – 69||Susan Goldsmith||Gyles Brandreth||Susie Dent||133|
|3731||30/06/2004||P||David Thirlwall||86 – 48||Jim Mitchell||Gyles Brandreth||Susie Dent||141|
|3732||1/07/2004||P||David Thirlwall||80 – 74||Graham Andrews||Gyles Brandreth||Susie Dent||133|
|3835||10/12/2004||QF||David Thirlwall||58 – 93||Jack Welsby||Rick Wakeman||Susie Dent||116|