Luke Hanrahan went to meet Eduard Payne and Rasheed Rollins, co-founders of the YouthDirect website.
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They said they wouldn't do it. But the Met Police couldn't resist the challenge set by their colleagues in Scotland.
The results of the first preference votes counted so far gives an early indication that Mr Khan is line to take power at City Hall.
Mr Goldsmith's campaign, run by Sir Lynton's communications firm has come under fire from Labour.