Starbucks is to charge customers 5p to use a paper cup at some of its stores.
The three-month trial, which is taking place at 35 London stores based across the city, the west end and west London, is part of a drive by the coffee chain to cut down on single-use paper cups.
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Proceeds from the 5p charge will be donated to environmental charity and behaviour change experts, Hubbub. It is also tracking the impact of the charge on customer behaviour, helping to reduce waste and encourage the use of reusable cups.
It comes as Starbucks-commissioned research found that 48% of people surveyed said they would carry a reusable cup which would help save money and reduce waste.
Simon Redfern of Starbucks Europe said: "We're hoping that this charge will remind customers to rethink their use of single-use plastic-lined cups, as it has with plastic bags.
"We've offered a reusable cup discount for 20 years, with only 1.8% of customers currently taking up this offer, so we're really interested in working with Hubbub to see how this charge could help to change behaviour and help to reduce waste."
Starbucks has offered a £1 reusable cup to customers since 2014.
Julian Kirby, of Friends of the Earth, said: "A small charge is proven to be effective at cutting waste, so this is welcome news, although it would be good to know Starbucks' plans for shifting to non-plastics alternatives.
"Alternatives do exist - and the in-store collection of disposable cups for recycling is certainly possible."