Out in the fourth group at 7:18am, Thomson carded a three-under-par 69 but it wasn’t until just before 8:30pm that her fate was sealed, after being involved in a play-off.
That involved 12 players battling for the final eight spots in the fourth women’s major of the season at Royal Lytham & St Annes, with Thomson staying in the hunt until the third extra hole.
By that time, the Aberdonian was fighting it out for the final spot with American Paula Creamer and Canadian Brittany Marchand but Thomson bowed out after they both made birdies there.
Marchand progressed when a par was good enough at the next, leaving Creamer as first reserve and now relying on a withdrawal to extend her record of having played in every British Open since 2005.
Joining Marchand in coming through the play-off was American Tiffany Joh, who led at the halfway stage in the Ladies Scottish Open after opening rounds of 62 and 67 at Gullane before crashing to a third-round 80.
Swedish amateur Linn Grant led the qualifiers with a stunning 10-under-par 62, reeling off five birdies in a row around the turn before storming home in 30 as she finished four shots clear of the field.
Her compatriot and fellow amateur, Frida Kinhault, also made it through with a four-under-par 68, the same score posted by Korea’s Haeji Kang, who found herself in the scramble for spots despite finishing joint third in the Ladies Scottish Open.
Meanwhile, Gavin Hay is hoping a return to Deer Park this week as a defending champion will kick-start his season. The 26-year-old is targeting a return to form in the Emtec Group Deer Park Masters, which he won 12 months ago in a play-off.
“With the summer we’ve had this year I think Deer Park will present a very different challenge this year compared to last year considering it rained both days,” said Hay. “I’m really looking forward to it and it would be the perfect time for my fortunes to turn around again.”