http://www.legislation.gov.uk/id/uksi/2008/631

PART 2Members of the Metropolitan Police Authority

Tenure of office20

1

Where the Mayor is appointed to be a member of the Metropolitan Police Authority under regulation 6 he shall cease to be a member of the Metropolitan Police Authority if he ceases to be Mayor and does not on the same day again become Mayor.

2

A member of the London Assembly appointed to be a member of the Metropolitan Police Authority under regulation 6 shall cease to be a member of the Metropolitan Police Authority if he ceases to be a member of the London Assembly and does not on the same day again become a member of the London Assembly.