Thornley won silver in the women's singles scull at the 2017 World ChampionshipsDates: 23 July-8 August Time in Tokyo: BST +8Coverage: Watch live on BBC TV, BBC iPlayer, BBC Red Button and online; Listen on BBC Radio 5 Live, Sports Extra and Sounds; live text and video clips on BBC Sport website and app.Great Britain failed to win an Olympic rowing gold for the first Games since 1984 as the men's eight crew took bronze in the final race of the Tokyo 2020 regatta.
The British eight were pipped to silver by Germany as New Zealand took gold.
Earlier, Britain's Vicky Thornley was edged out of a medal despite a late push in the women's single scull.
The 33-year-old Welsh rower finished 0.67 seconds behind Austria's Magdalena Lobnig in the race for bronze.
Britain have now finished fourth in six events at the Sea Forest Waterway.
Thornley, who won silver with Katherine Grainger in Rio 2016's double sculls, was bidding to become the first British woman to claim a medal in the event.
An emotional Thornley said she didn't think she could have "done anything more" after switching from the doubles.
Her journey to Tokyo was far from smooth, however.
The 2017 World Championship silver medallist was unable to defend her title the following year as a result of over-training, then broke her elbow in May last year after being knocked off her bike.
Thornley was involved in more road drama in May, having to run for her lifeexternal-link seconds before a car collided with another vehicle and caught fire.
"I set out to find out what it takes as an individual and I wanted to have a go in the single," she said.
"I've given it absolutely everything I've got in the last five years."
New Zealand's Emma Twigg cruised to gold in the single scull, with Hannah Prakatsen, representing the Russian Olympic Committee, taking silver.
"I knew I was racing for bronze, I'm not going to lie. I didn't think gold or silver were attainable," said Thornley.
"It was about me and Lobnig. I thought she would go out hard again but that I could reel her back in. Fair play to her, she's an awesome athlete.
"Maybe I let it get away a bit too much in the first bit but I was confident I could come through in the second half. In the last 100 I just fell away."
Grainger, in her role as an analyst for BBC television, said she was "so, so proud" of her former rowing partner.
"A lot of people wouldn't have expected her to get to the final, necessarily," said the five-time medallist.
"Although it is a fourth - again - that is history made. It is the highest any female scull has come at the Olympic Games."
