Transport for London is considering phasing out coins and notes next year and replacing them entirely with contactless payments - such as Oyster Cards.
TFL says it would help save millions of pounds. But thousands of people still rely on cash to travel around on London's buses every day, and critics warn it could put jobs and safety at risk.
Rags Martel reports:
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The high of 35C was recorded on a Bakerloo line train between Piccadilly Circus and Oxford Circus at 2pm.
Weather forecasters say temperatures could reach 35C, beating the previous record of 34.6C in the scorching summer of 1976.
After years of political manoeuvring over the future expansion of Heathrow Airport, there has been an important development this lunchtime.