Adverts for food and drink products high in fat, salt or sugar are now banned across London's public transport network, under a new scheme put forward by Sadiq Khan.
From today, promotion of the unhealthy products will no longer be allowed on the London Underground network, Overground network or on buses and bus shelters.
Instead, brands will only be able to place adverts which promote their healthier products.
- Read more: Junk food adverts to be banned across Transport for London network to combat child obesity
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The London mayor launched a public consultation on plans to ban the ads last May, saying action was needed to tackle the capital's "ticking time-bomb" of childhood obesity.
A total of 82 per cent of the 1,500 respondents supported the proposals.
London currently has one of the highest child overweight and obesity rates in Europe, with almost 40 per cent of children aged 10 and 11 overweight or obese.
Children from poorer areas of the capital are disproportionately affected, with young people in Barking and Dagenham almost twice as likely to be overweight as children from Richmond.