Mayor Boris Johnson will tell the Home Affairs Select Committee later how public confidence in policing can be restored.
It comes after revelations that undercover police officers sought to smear the family of Stephen Lawrence.
Met Police Commissioner Sir Bernard Hogan-Howe will also be appearing.
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Scotland Yard said two murder investigations have been launched following the separate incidents, which both happened in the past week.
Photos show the extraordinary surgical procedures to remove the growth.
The Met Police says 143 firearms have been handed in at stations across the capital in just seven days, including two antique machine guns.