Great Britain Paralympic shooter Di Coates missed out on a place in the final of the R2-10 metres air rifle standing by a single place on Thursday 30th August.
The 58-year-old, competing in her eighth Games, finished ninth with 389 points, falling short of the top-eight place required to progress by just two points.
The eight-time Paralympic medallist, holding back tears, said:
''It's quite disappointing, it's even more disappointing not to be on top of the pile where I should have been.''
Coates opened with scores of 99, 98 and 98, but slipped to 94 in her fourth and final series which proved costly She said:
''I was fine at the start. My nerves got to me at the end, especially in my last two shots where I struggled.''
Coates was pipped to eighth place by Elizabeth Kosmala, a 70-year-old grandmother from Australia who is the oldest competitor at London 2012.
''I was not focusing on my rivals,'' she added. ''I shoot for myself and focus on my round. It just didn't work for me today.''
The Hampshire shooter is the only British competitor to have previous experience of a home Games, having made her Paralympic debut at Stoke Mandeville. And she is now looking to make sure she has happy memories of this one by turning her attention to her second event, the R3 10m air rifle prone.
''I hope so,'' she said when asked if she would be able to refocus despite today's disappointment.
''They are totally different events. Unfortunately this wasn't my best event and all I can do is my best on the day.''
There was also disappointment for the host nation's two other competitors, with Karen Butler finishing 12th with 384 points and Mandy Pankhurst 16th with 380. The standard of competition was very high, though, with China's Zhang Cuiping qualifying in first place in a new Paralympic record of 396.