The Mayor will be trying out the new east London Overground extension this morning.
The new line from Clapham Junction to Surrey Quays, marks the completion of a £1.5 billion project to create an orbital service circling the whole of the capital.
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Corbyn was unveiling a poster less than a mile away as Khan gave his final campaign speech to party supporters in London.
Hay fever is an allergic reaction to airbourne pollen. There are 2 million sufferers in London (that's one in 5 people).
The man suffered head injuries after falling from Westminster Bridge and landing on concrete steps.