The claim:
City Hall funding has allowed the Met Police to fund “an extra 1,000 police officers than would otherwise be affordable" (source).
Analysis:
This is misleading. In fact, Sadiq Khan was planning to cut 1,000 officers and then U-turned. This decision did not increase police numbers but kept them level.
The number of police officers fell significantly when Sadiq Khan took power (source). Boris Johnson, as Mayor of London, maintained funding for 32,000 police officers when he was in office.
The numbers started only rising in recent years after the Government announced 20,000 new police officers across England and Wales (source). These increases in Met Police numbers were possible because of government funding, not Sadiq Khan.