The emergence of DeepSeek's artificial intelligence model has triggered shockwaves on Wall Street. Shares in major tech firms such as Nvidia fell sharply, with the chip giant losing almost $600bn in market value. Investors are questioning the high valuation and dominance of some established US firms. DeepSeek's AI model was developed for much less. We go to Beijing to learn more.

Also in the programme: The United Nations says hospitals are overwhelmed, treating hundreds of injured people in Goma in eastern Congo where Rwandan-backed M23 rebels are trying to capture the city from the Congolese army; plus the backstory of how Tetris became one of our most beloved computer games.

(Photo: DeepSeek logo and Chinese flag are seen in this illustration taken, January 28, 2025. Credit: Reuters/Dado Ruvic/Illustration)