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Today's episode is sponsored by Smart Travel, a podcast from NerdWallet.
Do you have a friend who treats airfare like a puzzle and somehow always ends up with a first class upgrade?
Smart Travel is like that friend, minus the group texts.
NerdWallet's travel journalists break down the pros and cons of travel decisions,
like when lounge access is worth paying for and which hotel loyalty programmes actually pay off.
Make your travel dollars work harder.
Follow Smart Travel on your favourite podcast app.
Welcome to The Inquiry from the BBC World Service.
I'm David Baker.
Each week, one question, four expert witnesses and an answer.
It's a shocking sight.
Images on Portugal's evening news program, Jornal de Noite,
zoom in on blood-filled syringes discarded near a children's playground in central Lisbon.
Men smoke crack in the street as shoppers squeeze past.
Drug dealers openly do business in side streets just minutes away from the city's tourist attractions.