A Metropolitan Police spokesman said the arrests were made over alleged public order offences.
Six males were arrested during the game at Millwall in relation to a banner being unfurled at the game. They remain in custody at this time."
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MPs say there must be no way back for the former London mayor as he hints he could seek to rejoin the party.
President Donald Trump has requested that the Justice Department investigates whether the FBI infiltrated his campaign.
High pressure will help keep conditions relatively quiet through the course of this week.