Around 40 members of the English Defence League are holding a demonstration outside Parliament today.
The group were denied permission to march through Walthamstow by the Home Secretary.
More top news
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.